A small, benign skin growth that may have a stalk (peduncle). Acrochordons most commonly appear on the neck, axillary, groin, and inframammary regions. Also called skin tag.

In genetics, describes an individual who has a particular phenotypic trait or disease. The individual expresses the trait or has signs and symptoms of the disease.

One of two or more versions of a genetic sequence at a particular region on a chromosome. An individual inherits two alleles for each gene, one from each parent.

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• Allele (National Human Genome Research Institute)

The presence of different variants at a single gene locus that cause the same or similar phenotypic expressions of a disease or condition.

The occurrence of one or more extra or missing chromosomes in a cell or organism. Aneuploidy refers to any chromosome number that is not an exact multiple of the haploid number of chromosomes (which is 23 in humans).

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• Can changes in the number of chromosomes affect health and development? (MedlinePlus)

A type of gene that regulates cell growth. When an antioncogene is mutated, uncontrolled cell growth may occur. This may contribute to the development of cancer. Also called tumor suppressor gene.

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• Tumor Suppressor Gene (National Human Genome Research Institute)

Procedures that use donor or nondonor eggs and sperm to create embryos in vitro. Examples of ART include in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian transfer (ZIFT). These procedures may be used prior to preimplantation genetic testing (PGT). Also called assisted reproductive technology.

One of two major ancestral groups of Jewish people whose ancestors lived in France and Central and Eastern Europe, including Germany, Poland, and Russia. The other group is called Sephardic Jews and includes those whose ancestors lived in Spain, Portugal, North Africa, and the Middle East. Most Jewish people living in the United States are of Ashkenazi descent.

Procedures that use donor or nondonor eggs and sperm to create embryos in vitro. Examples of assisted reproductive technology include in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian transfer (ZIFT). These procedures may be used prior to preimplantation genetic testing (PGT). Also called ART.

Proportion of a disease in exposed individuals that can be attributed to an exposure. In the context of genetic studies, the "exposure" is the frequency of a specific genetic variant.

Having to do with any of the 22 numbered pairs of chromosomes found in most human cells. Autosomal chromosomes are numbered 1-22. The sex chromosomes (X and Y chromosomes) determine whether an individual is male or female and are not considered autosomal chromosomes.

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• Autosome (National Human Genome Research Institute)

One of the ways a genetic trait or a genetic condition can be inherited. In autosomal dominant inheritance, a genetic condition occurs when a variant is present in only one allele (copy) of a given gene.

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• Autosomal Dominant (National Human Genome Research Institute)

One of the ways a genetic trait or a genetic condition can be inherited. In autosomal recessive inheritance, a genetic condition occurs when one variant is present on both alleles (copies) of a given gene.

When chromosomes at a particular stage in cell division are stained using one of several laboratory techniques, a specific pattern of light and dark stripes (bands) appears when the chromosomes are viewed through a microscope; the banding pattern assists in assigning each chromosome its particular number and evaluating its structure.

Two nitrogen-containing bases (or nucleotides) that pair together to form the structure of DNA. The four bases in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T). These bases form specific pairs (A with T, and G with C). Base pair may also refer to the actual number of base pairs, such as 8 base pairs, in a sequence of nucleotides.

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• Base Pair (National Human Genome Research Institute)

Of or pertaining to both alleles of a single gene (paternal and maternal). For example, biallelic mutation carriers have a mutation (not necessarily the same mutation) in both copies of a particular gene (a paternal and a maternal mutation).

In classical genetics, an individual who carries one deleterious allele for an autosomal recessive disorder. In clinical discussions, may refer to an individual who carries a deleterious allele that predisposes to disease.

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• Carrier (National Human Genome Research Institute)

The proportion of individuals in a population who have a single copy of a specific recessive genetic variant. Carrier frequency also sometimes refers to the prevalence of variants in dominantly acting genes, such as BRCA1 and BRCA2. Also called carrier rate.

The proportion of individuals in a population who have a single copy of a specific recessive genetic variant. Carrier rate also sometimes refers to the prevalence of variants in dominantly acting genes, such as BRCA1 and BRCA2. Also called carrier frequency.

The process of extending genetic testing to individuals at risk within a family for inheriting a pathogenic variant previously identified in a biologic relative. This process is repeated as more pathogenic variant carriers are identified within the family. Cascade genetic testing is sometimes referred to as cascade screening, although cascade genetic testing is the preferred term. Also called cascade testing.

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A systematic process for the identification of individuals within a family at risk for a hereditary condition. Cascade screening begins with finding a pathogenic/likely pathogenic variant through broad-based testing (such as full gene or multigene panel testing) in one family member, usually affected with the condition. Then, testing just for the specific family variant is extended to at-risk biologic relatives. This process is repeated as more affected individuals or pathogenic variant carriers are identified. Cascade screening is sometimes referred to as cascade testing (preferred term).

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• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

The process of extending genetic testing to individuals at risk within a family for inheriting a pathogenic variant previously identified in a biologic relative. This process is repeated as more pathogenic variant carriers are identified within the family. Cascade testing is sometimes referred to as cascade screening, although cascade testing is the preferred term. Also called cascade genetic testing.

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• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

The presence of somatic mutations in hematopoietic stem cells in an individual without a detectable hematologic cancer. The definition of CHIP requires that mutations are present with a variant allele frequency of 2% or higher and they are located in genes described to be affected in hematologic cancers. This condition is more common in older individuals and in those who have received treatment for other cancers. It is associated with both an increased risk of developing cardiovascular disease and hematologic cancers. Also called clonal hematopoiesis of indeterminate potential.

A genomic imbalance that occurs when a cell has an abnormal number of chromosomes. This can be caused by unexpected chromosomal crossover or by the presence of small, extra-chromosomal pieces of DNA.

A structure found inside the nucleus of a cell. A chromosome is made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes.

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• Chromosome (National Human Genome Research Institute)

A term that refers to the likelihood that a test will, by prompting an intervention, result in an improved health outcome. The clinical utility of a genetic test is based on the health benefits related to the interventions offered to individuals with positive test results.

A term that refers to the predictive value of a test for a given clinical outcome (e.g., the likelihood that cancer will develop in someone with a positive test). Clinical validity is primarily determined by the sensitivity and specificity with which a test identifies individuals with a defined clinical condition within a given population. The clinical validity of a genetic test is the likelihood that cancer will develop in someone with a positive test result.

The presence of somatic mutations in hematopoietic stem cells in an individual without a detectable hematologic cancer. The definition of clonal hematopoiesis of indeterminate potential requires that mutations are present with a variant allele frequency of 2% or higher and they are located in genes described to be affected in hematologic cancers. This condition is more common in older individuals and in those who have received treatment for other cancers. It is associated with both an increased risk of developing cardiovascular disease and hematologic cancers. Also called CHIP.

A variation in the number of copies of a particular sequence of DNA present in the genome of an individual. CNVs include insertions, deletions, and duplications of segments of DNA. They account for a significant number of the genetic variations between individuals. CNVs may also be associated with specific traits or disorders. Also called copy number variant.

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• Copy Number Variation (CNV) (National Human Genome Research Institute)

A sequence of three consecutive nucleotides in a DNA or RNA molecule that codes for a specific amino acid. Certain codons signal the start or end of translation. These are called start or stop (or termination) codons.

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• Codon (National Human Genome Research Institute)

The presence of two different mutated alleles at a particular gene locus.

Describes a condition or trait that is present at birth. Congenital conditions may be caused by genetic factors, non-genetic factors, or a combination of both.

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• Congenital (National Human Genome Research Institute)

Genetic relatedness between individuals who are descendants of at least one common ancestor.

A process of information exchange between a clinician and an individual or their legal proxy designed to facilitate autonomous, informed decision making. The informed consent process for genetic testing should include an explanation of the medical and psychosocial risks, benefits, limitations, and potential implications of genetic analysis, a discussion of privacy, confidentiality, the documentation and handling of genetic test results, as well as options for managing the hereditary disease risk. Also called informed consent.

Constitutional DNA refers to tissue derived from reproductive cells (egg or sperm) that become incorporated into the DNA of every cell in the body of the offspring. A germline mutation may be passed from parent to offspring. Also called germline DNA.

An individual who presents for genetic counseling.

A variation in the number of copies of a particular sequence of DNA present in the genome of an individual. Copy number variants include insertions, deletions, and duplications of segments of DNA. They account for a significant number of the genetic variations between individuals. Copy number variants may also be associated with specific traits or disorders. Also called CNV.

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• Copy Number Variation (CNV) (National Human Genome Research Institute)

The transmission, together, of 2 or more genes on the same chromosome, as a result of their being in very close physical proximity to one another (i.e., linked).

A benign tumor that arises from smooth muscle tissue in a hair follicle, forming a papule. Cutaneous leiomyomas (or leiomyomata) can be painful in the presence of cold or tactile stimuli.

Itchy papules that are brownish-red in color and typically appear on the shins, thighs, feet, or neck.

The study of the structure, function, and abnormalities of human chromosomes.

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• Cytogenetics (National Human Genome Research Institute)

A genetic alteration that is present for the first time in one family member as a result of a variant (or mutation) in a germ cell (egg or sperm) of one of the parents, or a variant that arises in the fertilized egg itself during early embryogenesis. Also called de novo variant, new mutation, and new variant.

A genetic alteration that is present for the first time in one family member as a result of a variant (or mutation) in a germ cell (egg or sperm) of one of the parents, or a variant that arises in the fertilized egg itself during early embryogenesis. Also called de novo mutation, new mutation, and new variant.

A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain. Also called disease-causing mutation, pathogenic variant, predisposing mutation, and susceptibility gene mutation.

A type of genetic change that involves the absence of a segment of DNA. It may be as small as a single base but can vary significantly in size.

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• Deletion (National Human Genome Research Institute)

The molecule inside cells that contains the genetic information responsible for the development and function of an organism. DNA molecules allow this information to be passed from one generation to the next. DNA is made up of a double-stranded helix held together by weak hydrogen bonds between purine-pyrimidine nucleotide base pairs: adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C). Also called DNA.

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• Deoxyribonucleic Acid (DNA) (National Human Genome Research Institute)
• What is DNA? (MedlinePlus)

Refers to the number of times a nucleotide is read during sequencing. A greater depth of coverage can increase confidence in the final results. Deep coverage aids in differentiating sequencing errors from single nucleotide polymorphisms. This can be specifically useful when a patient has a mosaicism or when a tumor is heterogeneous for a mutation.

A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain. Also called deleterious mutation, pathogenic variant, predisposing mutation, and susceptibility gene mutation.

The molecule inside cells that contains the genetic information responsible for the development and function of an organism. DNA molecules allow this information to be passed from one generation to the next. DNA is made up of a double-stranded helix held together by weak hydrogen bonds between purine-pyrimidine nucleotide base pairs: adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C). Also called deoxyribonucleic acid.

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• Deoxyribonucleic Acid (DNA) (National Human Genome Research Institute)
• What is DNA? (MedlinePlus)

A specific physical region or amino acid sequence in a protein that is associated with a particular function or corresponding segment of DNA.

The presence of two different mutated alleles at two separate genetic loci.

A set of clinical criteria that is used to stratify prostate cancers into three risk categories to estimate cancer growth and spread. The criteria include Gleason score, prostate-specific antigen level, and clinical stage at diagnosis.

A heritable change that does not affect the DNA sequence but results in a change in gene expression. Examples include promoter methylation and histone modifications. Also called epigenetic variant and epimutation.

A heritable change that does not affect the DNA sequence but results in a change in gene expression. Examples include promoter methylation and histone modifications. Also called epigenetic alteration and epimutation.

The study of heritable changes that do not affect the DNA sequence but influence gene expression.

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• Epigenetics (National Human Genome Research Institute)

A heritable change that does not affect the DNA sequence but results in a change in gene expression. Examples include promoter methylation and histone modifications. Also called epigenetic alteration and epigenetic variant.

ER-negative PR-negative HER2/neu-negative breast cancer is defined by a lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/neu). Also called TNBC and triple-negative breast cancer.

The sequence of DNA that is present in the final, mature messenger RNA transcript. Most exons code for amino acids, which link together to form a protein. Most genes are made up of many exons with introns in between them.

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• Exon (National Human Genome Research Institute)

A distinctive facial feature or expression that is characteristic of a specific condition.

A test result that indicates an individual is affected and/or has a certain gene mutation when he or she is actually unaffected and/or does not have the mutation; i.e., a positive test result in a truly unaffected or mutation-negative individual.

Having to do with a phenotype or trait that occurs with greater frequency in a given family than in the general population. Familial traits may be related to shared genetic factors and/or shared lifestyle or environmental factors.

A type of inherited disorder in which there is a higher-than-normal risk of certain types of cancer. Family cancer syndromes are caused by inherited genetic variants and may be associated with several clinical manifestations. Examples of family cancer syndromes include Lynch syndrome and hereditary breast and ovarian cancer syndrome. Also called hereditary cancer syndrome and inherited cancer syndrome.

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• Genetic Testing for Inherited Cancer Susceptibility Syndromes

A parent, sibling, or child of an individual. Also called first-degree relative.

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• First Degree Relative (National Human Genome Research Institute)

A benign tumor of the hair follicle that appears as a small, whitish papule. Fibrofolliculomas are typically found on the face, ears, neck, and upper torso. They are pathognomonic for Birt-Hogg-Dubé syndrome, a hereditary condition associated with the development of kidney cancer.

A parent, sibling, or child of an individual. Also called FDR.

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• First Degree Relative (National Human Genome Research Institute)

A technique used to identify the presence of specific chromosomes or chromosomal regions through hybridization (attachment) of fluorescently-labeled DNA probes to denatured chromosomal DNA. Examination through a microscope under fluorescent lighting detects the presence or absence of the colored hybridized signal, hence the presence or absence of the chromosome material. Also called fluorescence in situ hybridization.

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• Fluorescence In Situ Hybridization (FISH) (National Human Genome Research Institute)

A technique used to identify the presence of specific chromosomes or chromosomal regions through hybridization (attachment) of fluorescently-labeled DNA probes to denatured chromosomal DNA. Examination through a microscope under fluorescent lighting detects the presence or absence of the colored hybridized signal, hence the presence or absence of the chromosome material. Also called FISH.

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• Fluorescence In Situ Hybridization (FISH) (National Human Genome Research Institute)

A genetic alteration observed with high frequency in a group that is or was geographically or culturally isolated, in which one or more of the ancestors was a carrier of the altered gene. This phenomenon is often called a founder effect. Also called founder variant.

A genetic alteration observed with high frequency in a group that is or was geographically or culturally isolated, in which one or more of the ancestors was a carrier of the altered gene. This phenomenon is often called a founder effect. Also called founder mutation.

An insertion or deletion involving a number of base pairs that is not a multiple of three, which consequently disrupts the triplet reading frame of a DNA sequence. Such variants (or mutations) usually lead to the creation of a premature termination (stop) codon, and result in a truncated (shorter-than-normal) protein product. Also called frameshift variant.

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• Frameshift Mutation (National Human Genome Research Institute)

An insertion or deletion involving a number of base pairs that is not a multiple of three, which consequently disrupts the triplet reading frame of a DNA sequence. Such variants (or mutations) usually lead to the creation of a premature termination (stop) codon, and result in a truncated (shorter-than-normal) protein product. Also called frameshift mutation.

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• Frameshift Mutation (National Human Genome Research Institute)

The basic unit of heredity passed from parent to child. Genes are made up of sequences of DNA and are arranged, one after another, at specific locations on chromosomes in the nucleus of cells. They contain information for making specific proteins that lead to the expression of a particular physical characteristic or trait, such as hair color or eye color, or to a particular function in a cell.

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• Gene (National Human Genome Research Institute)
• The Genetics of Cancer

A phenomenon in which the signs and symptoms of some genetic conditions tend to become more severe and/or appear at an earlier age as the condition is passed from one generation to the next.

A communication process that seeks to assist affected or at-risk individuals and families in understanding the natural history, disease risks, and mode of transmission of a genetic disorder; to facilitate informed consent for genetic testing when appropriate; to discuss options for risk management and family planning; and to provide for or refer individuals for psychosocial support as needed.

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• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)
• Genetic Counseling (National Human Genome Research Institute)

A term used to describe different genetic mechanisms that produce the same or similar phenotypes. There are two types of genetic heterogeneity: allelic heterogeneity and locus heterogeneity. Allelic heterogeneity occurs when different variants at a single gene locus cause the same or similar phenotypic expressions of a disease or condition. Locus heterogeneity occurs when variants at different gene loci cause the same or similar phenotypic expressions of a disease or condition.

A sequence of DNA with a known physical location on a chromosome. Genetic markers and genes that are close to each other on a chromosome tend to be inherited together. Genetic markers vary between individuals to the extent that they can be used to help find a nearby gene causing a certain disease or trait within a family. Examples of genetic markers are single polymorphism nucleotides (SNPs), restriction fragment length polymorphisms (RFLPs), variable number of tandem repeats (VNTRs), microsatellites, and copy number variants (CNVs). Genetic markers may or may not have a known function.

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• Genetic Marker (National Human Genome Research Institute)

An increased chance or likelihood of developing a particular disease based on the presence of one or more genetic variants and/or a family history suggestive of an increased risk of the disease. Having a genetic predisposition does not mean an individual will develop the disease. Lifestyle and environmental factors can also affect an individual's risk of disease. Also called genetic susceptibility, hereditary predisposition, and inherited predisposition.

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• Genetic Testing for Inherited Cancer Susceptibility Syndromes
• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

The process of testing individuals in a given population to identify those who have an increased risk of having or developing a particular genetic disorder or carrying a genetic variant for a particular disorder.

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• Genetic Screening (National Human Genome Research Institute)

An increased chance or likelihood of developing a particular disease based on the presence of one or more genetic variants and/or a family history suggestive of an increased risk of the disease. Having a genetic susceptibility does not mean an individual will develop the disease. Lifestyle and environmental factors can also affect an individual's risk of disease. Also called genetic predisposition, hereditary predisposition, and inherited predisposition.

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• Genetic Testing for Inherited Cancer Susceptibility Syndromes
• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

An inherited syndrome that includes a dermatological (skin) phenotype.

A method used to identify inherited genetic variants associated with risk for a particular disease or trait. A genome-wide association study looks at the entire genome for genetic variants, usually single nucleotide polymorphisms (SNPs), that tend to occur more often in individuals with the disease or trait being studied than in those without the disease or trait. Also called GWAS.

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• Genome-Wide Association Studies (GWAS) (National Human Genome Research Institute)

An epigenetic process resulting in the inactivation of an allele depending on which parent it was inherited from. Genomic imprinting can have clinical relevance because it may affect the expression of a gene mutation (i.e., the phenotype) in the offspring of an affected parent depending on which parent is passing on the mutation.

A term that refers to the two alleles present at a specific locus in the genome. Genotype also refers to the entire genetic makeup of an individual.

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• Genotype (National Human Genome Research Institute)

A laboratory process in which an individual’s germline DNA is analyzed for specific nucleotides or bases to determine whether certain variants are present. Genotyping differs from sequencing in which all of the nucleotides comprising a specific length of DNA are assessed (e.g., within a gene, exome, or genome).

The cells from which eggs or sperm (i.e., gametes) are derived.

Germline DNA refers to tissue derived from reproductive cells (egg or sperm) that become incorporated into the DNA of every cell in the body of the offspring. A germline mutation may be passed from parent to offspring. Also called constitutional DNA.

A term that refers to the presence of a pathogenic variant that is confined to the ovaries or testes. Germline mosaicism occurs when some of the sperm cells in the testes or some of the egg cells in the ovaries carry a pathogenic variant that is not found in other cells of the body. This means that a parent may not develop a genetic condition but could pass it on to one or more of their children. Also called gonadal mosaicism.

A gene change in a reproductive cell (egg or sperm) that becomes incorporated into the DNA of every cell in the body of the offspring. A variant (or mutation) contained within the germline can be passed from parent to offspring, and is, therefore, hereditary. Also called germline variant.

A gene change in a reproductive cell (egg or sperm) that becomes incorporated into the DNA of every cell in the body of the offspring. A variant (or mutation) contained within the germline can be passed from parent to offspring, and is, therefore, hereditary. Also called germline mutation.

A term that refers to the presence of a pathogenic variant that is confined to the ovaries or testes. Gonadal mosaicism occurs when some of the sperm cells in the testes or some of the egg cells in the ovaries carry a pathogenic variant that is not found in other cells of the body. This means that a parent may not develop a genetic condition but could pass it on to one or more of their children. Also called germline mosaicism.

A method used to identify inherited genetic variants associated with risk for a particular disease or trait. A GWAS looks at the entire genome for genetic variants, usually single nucleotide polymorphisms (SNPs), that tend to occur more often in individuals with the disease or trait being studied than in those without the disease or trait. Also called genome-wide association study.

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• Genome-Wide Association Studies (GWAS) (National Human Genome Research Institute)

The situation that occurs when one copy of a gene is inactivated or deleted and the remaining functional copy of the gene is not adequate to produce the needed gene product to preserve normal function.

A set of closely linked genetic markers or DNA variations on a chromosome that tend to be inherited together.

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• Haplotype (National Human Genome Research Institute)

Describes an individual who has only one member of a chromosome pair or chromosome segment rather than the usual two. Hemizygosity is often used to describe X-linked genes in males who have only one X chromosome. This term is sometimes used in somatic cell genetics where cancer cell lines are often hemizygous for certain alleles or chromosomal regions.

A type of inherited disorder in which there is a higher-than-normal risk of certain types of cancer. Hereditary cancer syndromes are caused by inherited genetic variants and may be associated with several clinical manifestations. Examples of hereditary cancer syndromes include Lynch syndrome and hereditary breast and ovarian cancer syndrome. Also called family cancer syndrome and inherited cancer syndrome.

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• Genetic Testing for Inherited Cancer Susceptibility Syndromes

An increased chance or likelihood of developing a particular disease based on the presence of one or more genetic variants and/or a family history suggestive of an increased risk of the disease. Having a hereditary predisposition does not mean an individual will develop the disease. Lifestyle and environmental factors can also affect an individual's risk of disease. Also called genetic predisposition, genetic susceptibility, and inherited predisposition.

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• Genetic Testing for Inherited Cancer Susceptibility Syndromes
• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

The proportion of variation in a population trait that can be attributed to inherited genetic factors. Heritability estimates range from 0 to 1 and are often expressed as a percentage. A number close to 1 may be indicative of a highly heritable trait within a population. It should not be used to estimate risk on an individual basis.

A laboratory method used to detect sequence differences between normal DNA and the DNA to be tested. Heteroduplex analysis is commonly used to screen for point variants (mutations) in a gene but does not identify the exact location of the variant.

A statistical estimate of whether two genetic loci are physically near enough to each other (or “linked”) on a particular chromosome that they are likely to be inherited together. A heterogeneity logarithm of the odds score is calculated in the presence of locus heterogeneity (when the same phenotype can be caused by mutations in genes at different chromosomal loci). Also called HLOD score.

The presence of two different alleles at a particular gene locus. A heterozygous genotype may include one normal allele and one mutated allele or two different mutated alleles (compound heterozygote).

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• Heterozygous (National Human Genome Research Institute)

A statistical estimate of whether two genetic loci are physically near enough to each other (or “linked”) on a particular chromosome that they are likely to be inherited together. An HLOD score is calculated in the presence of locus heterogeneity (when the same phenotype can be caused by mutations in genes at different chromosomal loci). Also called heterogeneity logarithm of the odds score.

The presence of two identical alleles at a particular gene locus. A homozygous genotype may include two normal alleles or two alleles that have the same variant.

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• Homozygous (National Human Genome Research Institute)

Deficiency of melanin.

Penetrance refers to the likelihood that a clinical condition will occur when a particular genotype is present. A condition is said to show incomplete penetrance when some individuals who carry the pathogenic variant express the associated trait while others do not. Also called reduced penetrance.

A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called indeterminate result and uninformative result.

A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called inconclusive result and uninformative result.

In genetic testing, a test result that reveals definitively the presence or absence of the germline genetic alteration associated with the hereditary disorder being assessed. In linkage analysis, the ability to distinguish between maternally inherited and paternally inherited DNA markers (polymorphisms) within or near a given gene of interest.

A process of information exchange between a clinician and an individual or their legal proxy designed to facilitate autonomous, informed decision making. The informed consent process for genetic testing should include an explanation of the medical and psychosocial risks, benefits, limitations, and potential implications of genetic analysis, a discussion of privacy, confidentiality, the documentation and handling of genetic test results, as well as options for managing the hereditary disease risk. Also called consent process.

A type of inherited disorder in which there is a higher-than-normal risk of certain types of cancer. Inherited cancer syndromes are caused by inherited genetic variants and may be associated with several clinical manifestations. Examples of inherited cancer syndromes include Lynch syndrome and hereditary breast and ovarian cancer syndrome. Also called family cancer syndrome and hereditary cancer syndrome.

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• Genetic Testing for Inherited Cancer Susceptibility Syndromes

An increased chance or likelihood of developing a particular disease based on the presence of one or more genetic variants and/or a family history suggestive of an increased risk of the disease. Having an inherited predisposition does not mean an individual will develop the disease. Lifestyle and environmental factors can also affect an individual's risk of disease. Also called genetic predisposition, genetic susceptibility, and hereditary predisposition.

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• Genetic Testing for Inherited Cancer Susceptibility Syndromes
• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

A type of genetic change that involves the addition of a segment of DNA. It may be as small as a single base but can vary significantly in size.

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• Insertion (National Human Genome Research Institute)

The sequence of DNA in between exons that is initially copied into RNA, but is cut out of the final, mature messenger RNA transcript. Introns do not code for amino acids that make up the protein encoded by the gene.

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• Intron (National Human Genome Research Institute)

A chromosomal defect in which a segment of the chromosome breaks off and reattaches in the reverse direction.

An extended family.

Refers to the age at which a disease phenotype is expressed in an individual who carries a pathogenic variant. Conditions with late or variable onset generally manifest later in life or at no fixed time over the course of a lifetime.

Where alleles (DNA markers) occur together more often than can be accounted for by chance because of their physical proximity on a chromosome. Also called linkage disequilibrium.

The tendency for genes or other segments of DNA to be inherited together during meiosis because of their location near one another on the same chromosome. Finding linked genes can help identify a disease-causing gene.

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• Linkage (National Human Genome Research Institute)

A gene-hunting technique that traces patterns of disease in high-risk families. Linkage analysis attempts to locate a disease-causing gene by identifying genetic markers of known chromosomal location that are co-inherited with the gene or trait of interest.

Where alleles (DNA markers) occur together more often than can be accounted for by chance because of their physical proximity on a chromosome. Also called LD.

The physical location of a specific gene on a chromosome.

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• Locus (National Human Genome Research Institute)

The presence of variants at different gene loci that cause the same or similar phenotypic expressions of a disease or condition.

A statistical estimate of whether two genetic loci are physically near enough to each other (or "linked") on a particular chromosome that they are likely to be inherited together. A LOD score of 3 or higher is generally understood to mean that two genes are located close to each other on the chromosome. In terms of significance, a LOD score of 3 means the odds are 1,000:1 that the two genes are linked and therefore inherited together. Also called logarithm of the odds score.

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• LOD Score (National Human Genome Research Institute)

A statistical estimate of whether two genetic loci are physically near enough to each other (or "linked") on a particular chromosome that they are likely to be inherited together. A logarithm of the odds score of 3 or higher is generally understood to mean that two genes are located close to each other on the chromosome. In terms of significance, a logarithm of the odds score of 3 means the odds are 1,000:1 that the two genes are linked and therefore inherited together. Also called LOD score.

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• LOD Score (National Human Genome Research Institute)

If there is one normal and one abnormal allele at a particular locus, as might be seen in an inherited autosomal dominant cancer susceptibility disorder, loss of the normal allele produces a locus with no normal function. When the loss of heterozygosity involves the normal allele, it creates a cell that is more likely to show malignant growth if the altered gene is a tumor suppressor gene. Also called loss of heterozygosity.

If there is one normal and one abnormal allele at a particular locus, as might be seen in an inherited autosomal dominant cancer susceptibility disorder, loss of the normal allele produces a locus with no normal function. When the loss of heterozygosity involves the normal allele, it creates a cell that is more likely to show malignant growth if the altered gene is a tumor suppressor gene. Also called LOH.

A high-throughput method used to determine a portion of the nucleotide sequence of an individual’s genome. This technique utilizes DNA sequencing technologies that are capable of processing multiple DNA sequences in parallel. Also called next-generation sequencing and NGS.

Benign pigmented patches that are commonly found on the lips. They may also be found inside the mouth, on the fingers, or on the genitalia. Melanocytic macules are a characteristic feature of Peutz-Jeghers syndrome, which is a hereditary syndrome associated with several types of cancer.

A term used to describe a new or second primary cancer that develops months or years after a first primary cancer, either in the same organ or in a different organ.

Genetic tests that use next-generation sequencing to test multiple genes simultaneously. Also called multigene panel test and multigene test.

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• Biomarker Testing for Cancer Treatment
• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

Repetitive segments of DNA scattered throughout the genome in noncoding regions between genes or within genes (introns). Microsatellites are often used as markers for linkage analysis because of their naturally occurring high variability in repeat number between individuals. These regions are inherently genetically unstable and susceptible to mutations.

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• Microsatellite (National Human Genome Research Institute)

A characteristic of cells that contain an abnormality in DNA mismatch repair. The presence of microsatellite instability can be a marker of a germline pathogenic variant in one of the DNA mismatch repair genes, as in the case of Lynch syndrome. Microsatellite instability can also occur sporadically. Also called MSI.

A genetic alteration in which a single base pair substitution alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position. Some missense variants (or mutations) will alter the function of the protein. Also called missense variant.

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• Missense Mutation (National Human Genome Research Institute)

A genetic alteration in which a single base pair substitution alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position. Some missense variants (or mutations) will alter the function of the protein. Also called missense mutation.

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• Missense Mutation (National Human Genome Research Institute)

A laboratory method commonly used for the detection of unusual copy number changes (insertions or deletions) of genomic sequences. Also called multiplex ligation-dependent probe amplification.

The manner in which a genetic trait, disorder, or risk of disorder is passed from one generation to the next. There are different modes of inheritance, and each mode of inheritance may result in a characteristic pattern of affected, unaffected, or at-risk individuals within a family. Examples are autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, and multifactorial inheritance.

The occurrence of 2 or more cell lines with different genetic or chromosomal make-up, within a single individual or tissue.

A characteristic of cells that contain an abnormality in DNA mismatch repair. The presence of MSI can be a marker of a germline pathogenic variant in one of the DNA mismatch repair genes, as in the case of Lynch syndrome. MSI can also occur sporadically. Also called microsatellite instability.

A benign tumor of nerve tissue commonly found on the tongue, lips, or in the gastrointestinal tract. Mucosal neuromas are a characteristic feature of multiple endocrine neoplasia type 2B (also known as MEN3), which is a hereditary syndrome associated with the development of medullary thyroid cancer.

Genetic tests that use next-generation sequencing to test multiple genes simultaneously. Also called MGPT and multigene test.

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• Biomarker Testing for Cancer Treatment
• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

Genetic tests that use next-generation sequencing to test multiple genes simultaneously. Also called MGPT and multigene panel test.

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• Biomarker Testing for Cancer Treatment
• Cancer Genetics Risk Assessment and Counseling (Health Professional Version)

A laboratory method commonly used for the detection of unusual copy number changes (insertions or deletions) of genomic sequences. Also called MLPA.

A change in the usual DNA sequence at a particular gene locus. Although the term often has a negative connotation, mutations (including polymorphisms) can be harmful, beneficial, or neutral in their effect on cell function. The term variant is sometimes used as a synonym for the term mutation.

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• Mutation (National Human Genome Research Institute)

A germline genetic testing method targeted to detect a specific variant or mutation (such as a deleterious MSH2 variant previously identified in a family), panel of variants (such as the 3 BRCA pathogenic variants comprising the founder mutation panel for individuals of Ashkenazi Jewish ancestry) or type of variant (such as large deletions or insertions in the BRCA1 gene). This type of testing is distinct from complete gene sequencing or variant scanning. The latter are designed to detect most variants in the region being tested. Current usage also applies this term to any genetic test.

Distortion or malformation of the fingernails and toenails. Also called onychodystrophy.

The likelihood that an individual with a negative test result is truly unaffected and/or does not have the particular gene mutation in question. Also called NPV.

A genetic alteration that is present for the first time in one family member as a result of a variant (or mutation) in a germ cell (egg or sperm) of one of the parents, or a variant that arises in the fertilized egg itself during early embryogenesis. Also called de novo mutation, de novo variant, and new variant.

A genetic alteration that is present for the first time in one family member as a result of a variant (or mutation) in a germ cell (egg or sperm) of one of the parents, or a variant that arises in the fertilized egg itself during early embryogenesis. Also called de novo mutation, de novo variant, and new mutation.

A high-throughput method used to determine a portion of the nucleotide sequence of an individual’s genome. This technique utilizes DNA sequencing technologies that are capable of processing multiple DNA sequences in parallel. Also called massively parallel sequencing and NGS.

A high-throughput method used to determine a portion of the nucleotide sequence of an individual’s genome. This technique utilizes DNA sequencing technologies that are capable of processing multiple DNA sequences in parallel. Also called massively parallel sequencing and next-generation sequencing.

An individual who does not carry a mutation previously identified in his or her family.

A research study that is designed to determine whether one intervention is not worse than another control intervention by a predetermined margin. An intervention that yields outcomes which are equivalent to or better than the control intervention is considered not inferior to the control intervention. Noninferiority studies are often conducted to examine whether a new, experimental treatment is not worse than an established standard of care.

An instance in which an individual has a trait-associated or disease-causing genetic variant, but the individual does not have the phenotype or condition. An example of nonpenetrance is a woman with a BRCA1 pathogenic variant who lives to be elderly and never develops breast or ovarian cancer.

A genetic alteration that causes the premature termination of a protein. The altered protein may be partially or completely inactivated, resulting in a change or loss of protein function. Also called nonsense variant.

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• Nonsense Mutation (National Human Genome Research Institute)

A genetic alteration that causes the premature termination of a protein. The altered protein may be partially or completely inactivated, resulting in a change or loss of protein function. Also called nonsense mutation.

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• Nonsense Mutation (National Human Genome Research Institute)

A newly discovered, distinct genetic alteration; NOT the same as new or de novo variant (or mutation). Also called novel variant.

A newly discovered, distinct genetic alteration; NOT the same as new or de novo variant (or mutation). Also called novel mutation.

The likelihood that an individual with a negative test result is truly unaffected and/or does not have the particular gene mutation in question. Also called negative predictive value.

A molecule that is the basic building block of the nucleic acids DNA and RNA. A nucleotide is made up of a nitrogen-containing base (adenine, guanine, thymine, and cytosine in DNA, and adenine, guanine, uracil, and cytosine in RNA), a phosphate group, and a sugar molecule (deoxyribose in DNA, and ribose in RNA). DNA and RNA are polymers made up of many nucleotides.

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• Nucleotide (National Human Genome Research Institute)

A DNA sequence variation that results in no gene product. The gene product (RNA or protein) of a null allele is either absent or not detectable at the molecular level or does not function at the phenotypic level.

Distortion or malformation of the fingernails and toenails. Also called nail dystrophy.

A benign growth of epithelial cells in the mouth or on the lips. This condition is associated with Cowden syndrome, which is a hereditary syndrome associated with the development of several types of cancer.

A small depression in the skin on the palm of the hand. Depressions may also be seen on the sole of the foot (plantar pits). They are usually pink or flesh-colored and range from 2 to 3 mm in diameter and 1 to 3 mm in depth. Palmar pits are often more visible after a brief soaking of the hands or feet. This condition is associated with basal cell nevus syndrome, which is a hereditary syndrome associated with the development of basal cell carcinoma.

A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain. Also called deleterious mutation, disease-causing mutation, predisposing mutation, and susceptibility gene mutation.

Findings that are distinctive or characteristic of a particular disease or condition and can be used to make a diagnosis.

A common laboratory technique used during molecular genetic testing to produce many copies of a specific sequence of DNA . PCR allows these DNA sequences to be amplified so there is a sufficient quantity of DNA to be analyzed by molecular genetic tests. Also called polymerase chain reaction.

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• Polymerase Chain Reaction (PCR) (National Human Genome Research Institute)

A diagram of family history that uses standardized symbols. A pedigree shows relationships between family members and indicates which individuals have certain genetic pathogenic variants, traits, and diseases within a family as well as vital status. A pedigree can be used to determine disease inheritance patterns within a family.

Penetrance refers to the likelihood that a clinical condition will occur when a particular genotype is present. For adult-onset diseases, penetrance is usually described by the individual carrier's age, sex, and organ site. For example, the penetrance for breast cancer in female carriers of BRCA1 pathogenic variants is often quoted by age 50 years and by age 70 years.

A phenotypic trait or disease that resembles the trait expressed by a particular genotype but in an individual who is not a carrier of that genotype.

The observable characteristics or traits in an individual based on the expression of their genes. The phenotype is determined by the individual's genotype and possibly influenced by other factors, such as environmental factors or other genetic modifiers.

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• Phenotype (National Human Genome Research Institute)

A small depression in the skin on the sole of the foot. Depressions may also be seen on the palm of the hand (palmar pits). They are usually pink or flesh-colored and range from 2 to 3 mm in diameter and 1 to 3 mm in depth. Plantar pits are often more visible after a brief soaking of the hands or feet. This condition is associated with basal cell nevus syndrome, which is a hereditary syndrome associated with the development of basal cell carcinoma.

Irregular patterns of reddish brown pigmentation of the skin associated with sun exposure, aging, or a genetic cause.

A genetic alteration caused by the substitution of a single nucleotide for another nucleotide. Also called point variant.

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• Point Mutation (National Human Genome Research Institute)

A genetic alteration caused by the substitution of a single nucleotide for another nucleotide. Also called point mutation.

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• Point Mutation (National Human Genome Research Institute)

An assessment of the risk of a specific condition based on the collective influence of many genetic variants. These can include variants associated with genes of known function and variants not known to be associated with genes relevant to the condition. Also called PRS.

A common laboratory technique used during molecular genetic testing to produce many copies of a specific sequence of DNA . Polymerase chain reaction allows these DNA sequences to be amplified so there is a sufficient quantity of DNA to be analyzed by molecular genetic tests. Also called PCR.

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• Polymerase Chain Reaction (PCR) (National Human Genome Research Institute)

A common variant in a specific sequence of DNA. “Common” is typically defined as an allele frequency of at least 1% in the general population.

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• Polymorphism (National Human Genome Research Institute)

The likelihood that an individual with a positive test result truly has the particular gene and/or disease in question. Also called PPV.

The likelihood that an individual with a positive test result truly has the particular gene and/or disease in question. Also called positive predictive value.

A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain. Also called deleterious mutation, disease-causing mutation, pathogenic variant, and susceptibility gene mutation.

Genetic testing performed in an individual who does not show symptoms of the disorder, but who is at risk of developing the disorder.

The first individual in a family to be identified as possibly having a genetic disorder or condition.

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• Proband (National Human Genome Research Institute)

An assessment of the risk of a specific condition based on the collective influence of many genetic variants. These can include variants associated with genes of known function and variants not known to be associated with genes relevant to the condition. Also called polygenic risk score.

A DNA sequence that resembles a gene but has been mutated into an inactive form over the course of evolution. It often lacks introns and other essential DNA sequences necessary for function. Though genetically similar to the original functional gene, pseudogenes do not result in functional proteins, although some may have regulatory effects.

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• Pseudogene (National Human Genome Research Institute)

In genetics, the likelihood that a hereditary trait or disorder present in one family member will occur again in other family members. This is distinguished from recurrence risk for cancer, which is the chance that a cancer that has been treated will recur.

Penetrance refers to the likelihood that a clinical condition will occur when a particular genotype is present. A condition is said to show incomplete penetrance when some individuals who carry the pathogenic variant express the associated trait while others do not. Also called incomplete penetrance.

The quantitative or qualitative assessment of an individual’s risk of carrying a certain gene mutation, or developing a particular disorder, or of having a child with a certain disorder; sometimes done by using mathematical or statistical models incorporating such factors as personal health history, family medical history and ethnic background.

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• Risk Factors for Cancer

The process by which introns (noncoding regions of genes) are cut out of the primary messenger RNA transcript, and the exons (coding regions of genes) are joined together to make mature messenger RNA. Mature messenger RNA carries the instructions a cell needs for making a specific protein.

A low-throughput laboratory method used to determine the nucleotide sequence of a piece of DNA. Sanger sequencing uses polymerase chain reaction (PCR) to amplify the target DNA region and then sequences the PCR products.

Checking for disease in individuals who have no symptoms. Since screening may find diseases at an early stage, there may be a better chance of curing the disease. Screening may also include genetic testing to check for an individual's risk of developing an inherited disease.

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• Cancer Screening
• PDQ® Cancer Information Summaries: Screening/Detection (Testing for Cancer)

An aunt, uncle, grandparent, grandchild, niece, nephew, or half-sibling of an individual. Also called second-degree relative.

A benign yellow or flesh-colored lesion originating from an oil gland in the skin. Sebaceomas are typically found on the face or neck. They may be associated with Muir-Torre syndrome, which is a hereditary syndrome associated with the development of several types of cancer. Also called sebaceous epithelioma.

A benign yellow or flesh-colored lesion originating from an oil gland in the skin. Sebaceous epitheliomas are typically found on the face or neck. They may be associated with Muir-Torre syndrome, which is a hereditary syndrome associated with the development of several types of cancer. Also called sebaceoma.

An aunt, uncle, grandparent, grandchild, niece, nephew, or half-sibling of an individual. Also called SDR.

The process of fitting formal genetic models to data on expressed disease characteristics (phenotype) in biological family members in order to determine the most likely mode of inheritance for the trait or disease under study.

The frequency with which a test shows a true positive result among individuals who actually have the disease or the genetic variant in question. A test with high sensitivity has a low false-negative rate, which means it does a good job of correctly identifying affected individuals or carriers of a genetic variant.

A DNA sequence variation that occurs when a single nucleotide (adenine, thymine, cytosine, or guanine) is different from the reference sequence. Single nucleotide polymorphisms are usually present in at least 1% of the population and are the most common type of genetic variation among people. Single nucleotide polymorphisms may increase the risk of developing certain diseases, act as biomarkers to help predict the risk of developing certain diseases or how a person may respond to certain drugs, or be used to track the inheritance of disease-causing variants within families. Also called SNP.

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• Single Nucleotide Polymorphisms (SNPs) (National Human Genome Research Institute)

A DNA sequence variation that occurs when a single nucleotide (adenine, thymine, cytosine, or guanine) in the genome sequence is altered. Single nucleotide variants may be rare or common in a population. Sometimes single nucleotide variants are referred to as single nucleotide polymorphisms if they are present in at least 1% of the population. Also called SNV.

Mitotic crossover between homologous chromosomes.

A small, benign skin growth that may have a stalk (peduncle). Skin tags most commonly appear on the neck, axillary, groin, and inframammary regions. Also called acrochordon.

A DNA sequence variation that occurs when a single nucleotide (adenine, thymine, cytosine, or guanine) is different from the reference sequence. SNPs are usually present in at least 1% of the population and are the most common type of genetic variation among people. SNPs may increase the risk of developing certain diseases, act as biomarkers to help predict the risk of developing certain diseases or how a person may respond to certain drugs, or be used to track the inheritance of disease-causing variants within families. Also called single nucleotide polymorphism.

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• Single Nucleotide Polymorphisms (SNPs) (National Human Genome Research Institute)

A DNA sequence variation that occurs when a single nucleotide (adenine, thymine, cytosine, or guanine) in the genome sequence is altered. SNVs may be rare or common in a population. Sometimes SNVs are referred to as single nucleotide polymorphisms if they are present in at least 1% of the population. Also called single nucleotide variant.

A genetic alteration that occurs after conception and is not present within the germline. Somatic mutations can occur in any of the cells of the body except the germ cells (sperm and egg cells). An individual who has a somatic mutation cannot pass it on to their children. Some somatic mutations may lead to cancer or other diseases. Also called somatic variant.

A genetic alteration that occurs after conception and is not present within the germline. Somatic variants can occur in any of the cells of the body except the germ cells (sperm and egg cells). An individual who has a somatic variant cannot pass it on to their children. Some somatic variants may lead to cancer or other diseases. Also called somatic mutation.

Electrophoresis-based technique used in genetic testing to detect large deletions in DNA that can be missed by PCR-based genetic testing methods.

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• Southern Blot (National Human Genome Research Institute)

The frequency with which a test shows a true negative result among individuals who do not have the disease or the genetic variant in question. A test with high specificity has a low false-positive rate, which means it does a good job of correctly identifying unaffected individuals or noncarriers of a genetic variant.

A genetic alteration in the DNA sequence that occurs at the boundary of an exon and an intron (splice site). This change can disrupt RNA splicing resulting in the loss of exons or the inclusion of introns and an altered protein-coding sequence. Also called splice-site variant.

A genetic alteration in the DNA sequence that occurs at the boundary of an exon and an intron (splice site). This change can disrupt RNA splicing resulting in the loss of exons or the inclusion of introns and an altered protein-coding sequence. Also called splice-site mutation.

Cancer that occurs in people who do not have an inherited genetic variant that would increase their risk for that cancer. Sporadic cancer is sometimes used to differentiate cancers that occur in these people from cancers that occur in people who are known or likely to carry a high-risk variant that increases their risk for cancer. Sporadic cancer is also sometimes used to describe cancer that occurs in people who do not have a family history of that cancer or other associated cancers.

The summation of all positive pedigree LOD scores (statistical estimates of whether two genetic loci are physically near enough to each other on a particular chromosome that they are likely to be inherited together) at each point in the genome. Also called summary logarithm of the odds score.

The summation of all positive pedigree LOD scores (statistical estimates of whether two genetic loci are physically near enough to each other on a particular chromosome that they are likely to be inherited together) at each point in the genome. Also called sumLOD score.

In medicine, the ongoing evaluation of an individual who has an increased risk of developing a disease or who has a disease that appears to be clinically stable or not progressing. Surveillance is also used to find early signs that a disease has come back. In public health, surveillance may also refer to the ongoing systematic collection and analysis of information about the incidence, prevalence, morbidity, survival, and mortality related to a disease or health-related event in a certain group of people.

A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain. Also called deleterious mutation, disease-causing mutation, pathogenic variant, and predisposing mutation.

A term used to describe a new or second primary cancer that develops at the same time as the first primary cancer, either in the same organ or in a different organ with the same molecular basis. Synchronous cancer is not considered metastatic relapse.

A first cousin, great-grandparent, great-aunt, great-uncle, great-niece, great-nephew, great-grandchild, half-aunt, or half-uncle of an individual. Also called third-degree relative.

The end of a chromosome. Telomeres are made of repetitive sequences of non-coding DNA that protect the chromosome from damage. Telomeres become shorter each time the cell divides.

A first cousin, great-grandparent, great-aunt, great-uncle, great-niece, great-nephew, great-grandchild, half-aunt, or half-uncle of an individual. Also called TDR.

The amount of information, people, or materials that is put through a process during a specific period of time. In medicine, throughput can be used to describe the number of laboratory tests, such as genetic sequencing, performed or the number of patients seen in a clinic during a certain period of time.

TNBC is defined by a lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/neu). Also called ER-negative PR-negative HER2/neu-negative breast cancer and triple-negative breast cancer.

The process of synthesizing messenger RNA (mRNA) from DNA.

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• Transcription (National Human Genome Research Institute)

The process of synthesizing an amino acid sequence (protein product) from the messenger RNA (mRNA) code.

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• Translation (National Human Genome Research Institute)

A type of chromosomal abnormality in which a chromosome breaks and a portion of it reattaches to a different chromosomal location.

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• Translocation (National Human Genome Research Institute)

A benign tumor arising from the outer cells of the hair follicle.

A sequence of three nucleotides that is repeated a number of times in a row in a segment of DNA. A certain amount of variation in the number of trinucleotide repeats is common and usually does not cause disease in individuals. But too many copies of certain trinucleotide repeats in the DNA can affect the gene's function, which could lead to certain genetic disorders. The number of trinucleotide repeats can change as the gene is passed from parent to child.

Triple-negative breast cancer is defined by a lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/neu). Also called ER-negative PR-negative HER2/neu-negative breast cancer and TNBC.

The presence of an extra chromosome in some or all of the body's cells. This results in a total of three copies of that chromosome instead of the normal two copies. For example, Down syndrome (trisomy 21) is caused by having three copies of chromosome 21 instead of the usual two copies.

Sequencing of somatic tissue, such as tumors, refers to looking for variants in DNA that typically occur after conception. Somatic mutations can occur in any of the cells of the body except the germ cells (sperm and egg) and therefore are not passed on to children. These variants can (but do not always) cause cancer or other diseases.

A type of gene that regulates cell growth. When a tumor suppressor gene is mutated, uncontrolled cell growth may occur. This may contribute to the development of cancer. Also called antioncogene.

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• Tumor Suppressor Gene (National Human Genome Research Institute)

In genetics, describes an individual who does not have a particular phenotypic trait or disease.

A variation in a genetic sequence for which the association with disease risk is unclear. Also called variant of uncertain significance, variant of unknown significance, and VUS.

A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called inconclusive result and indeterminate result.

Variation in the traits, signs, or symptoms that can occur in individuals with the same condition. When there is variable expressivity, the trait may vary in clinical expression from mild to severe.

An alteration in the most common DNA nucleotide sequence. The term variant can be used to describe an alteration that may be benign, pathogenic, or of unknown significance. The term variant is increasingly being used in place of the term mutation.

A variation in a genetic sequence for which the association with disease risk is unclear. Also called unclassified variant, variant of unknown significance, and VUS.

A variation in a genetic sequence for which the association with disease risk is unclear. Also called unclassified variant, variant of uncertain significance, and VUS.

A variation in a genetic sequence for which the association with disease risk is unclear. Also called unclassified variant, variant of uncertain significance, and variant of unknown significance.

A laboratory process that is used to determine the nucleotide sequence primarily of the exonic (or protein-coding) regions of an individual’s genome and related sequences, representing approximately 1% of the complete DNA sequence. Also called whole exome sequencing and WXS.

A laboratory process that is used to determine nearly all of the approximately 3 billion nucleotides of an individual’s complete DNA sequence, including non-coding sequence. Also called whole genome sequencing.

A laboratory process that is used to determine the nucleotide sequence primarily of the exonic (or protein-coding) regions of an individual’s genome and related sequences, representing approximately 1% of the complete DNA sequence. Also called WES and WXS.

A laboratory process that is used to determine nearly all of the approximately 3 billion nucleotides of an individual’s complete DNA sequence, including non-coding sequence. Also called WGS.

A laboratory process that is used to determine the nucleotide sequence primarily of the exonic (or protein-coding) regions of an individual’s genome and related sequences, representing approximately 1% of the complete DNA sequence. Also called WES and whole exome sequencing.

X-linked dominant inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A single copy of the mutation is enough to cause the disease in both males (who have one X chromosome) and females (who have two X chromosomes). In some conditions, the absence of a functional gene results in the death of affected males.

X-linked recessive inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A male carrying such a mutation will be affected, because he carries only one X chromosome. A female carrying a mutation in one gene, with a normal gene on the other X chromosome, is generally unaffected.