NCI Dictionary of Genetics Terms

25 results found for: C

carrier: (KAYR-ee-er); 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.
carrier frequency: (KAYR-ee-er FREE-kwen-see); 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.
carrier rate: (KAYR-ee-er rayt); 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.
cascade genetic testing: (kas-KADE jeh-NEH-tik TES-ting); 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.
cascade screening: (kas-KADE SKREE-ning); 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).
cascade testing: (kas-KADE TES-ting); 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.
CHIP: 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.
chromosomal instability: (KROH-muh-SOH-mul IN-stuh-BIH-lih-tee); 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.
chromosome: (KROH-muh-some); 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.
clinical utility: (KLIH-nih-kul yoo-TIH-lih-tee); 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.
clinical validity: (KLIH-nih-kul vuh-LIH-dih-tee); 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.
clonal hematopoiesis of indeterminate potential: (KLOH-nul hee-MA-toh-poy-EE-sis ... IN-deh-TER-mih-nut poh-TEN-shul); 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.
CNV: 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.
codon: (KOH-don); 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.
compound heterozygosity: (KOM-pownd HEH-teh-roh-zy-GAH-sih-tee); The presence of two different mutated alleles at a particular gene locus.
congenital: (kun-JEH-nih-tul); 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.
consanguinity: (KON-sang-GWIH-nih-tee); Genetic relatedness between individuals who are descendants of at least one common ancestor.
consent process: (kun-SENT PRAH-ses); 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: (KAWNT-stuh-TOO-shuh-nul...); 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.
consultand: (kon-SUL-tand); An individual who presents for genetic counseling.
copy number variant: (KAH-pee NUM-ber VAYR-ee-unt); 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.
cosegregation: (KOH-seh-greh-GAY-shun); 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).
cutaneous leiomyoma: (kyoo-TAY-nee-us LY-oh-my-OH-muh); 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.
cutaneous lichen amyloidosis: (kyoo-TAY-nee-us LY-ken A-muh-loy-DOH-sis); Itchy papules that are brownish-red in color and typically appear on the shins, thighs, feet, or neck.
cytogenetics: (SY-toh-jeh-NEH-tix); The study of the structure, function, and abnormalities of human chromosomes.