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NCI Dictionary of Genetics Terms

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11 results found for: A



  • affected  listen  (uh-FEK-ted)
    Individuals in a pedigree who exhibit the specific phenotype under study.

  • allele  listen  (uh-LEEL)
    One of two or more DNA sequences occurring at a particular gene locus. Typically one allele (“normal” DNA sequence) is common, and other alleles (mutations) are rare.

  • allelic heterogeneity  listen  (uh-LEE-lik HEH-teh-roh-jeh-NEE-ih-tee)
    Different mutations in the same gene that cause different phenotypic manifestations or severity of disease.

  • aneuploidy  listen  (AN-yoo-PLOY-dee)
    The occurrence of one or more extra or missing chromosomes leading to an unbalanced chromosome complement, or any chromosome number that is not an exact multiple of the haploid number (which is 46).

  • ART 
    A term used to describe collectively a number of noncoital methods of conception that are used to treat infertility with donor or nondonor eggs and sperm including in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian transfer (ZIFT). Also called assisted reproductive technology.

  • Ashkenazi Jews  listen  (ASH-keh-NAH-zee jooz)
    One of two major ancestral groups of Jewish individuals, comprised of those whose ancestors lived in Central and Eastern Europe (e.g., Germany, Poland, Russia). The other group is designated Sephardic Jews and includes those whose ancestors lived in North Africa, the Middle East, and Spain. Most Jews living in the United States are of Ashkenazi descent.

  • assisted reproductive technology  listen  (uh-SIS-ted REE-proh-DUK-tiv tek-NAH-loh-jee)
    A term used to describe collectively a number of noncoital methods of conception that are used to treat infertility with donor or nondonor eggs and sperm including in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian transfer (ZIFT). Also called ART.

  • attributable risk  listen  (uh-TRIH-byoo-tuh-bul …)
    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.

  • autosomal  listen  (AW-toh-SOH-mul)
    Refers to any of the chromosomes numbered 1-22 or the genes on chromosomes 1-22. This term excludes the sex-determining chromosomes, X and Y.

  • autosomal dominant  listen  (AW-toh-SOH-mul DAH-mih-nunt)
    Autosomal dominant inheritance refers to genetic conditions that occur when a mutation is present in one copy of a given gene (i.e., the person is heterozygous).

  • autosomal recessive  listen  (AW-toh-SOH-mul reh-SEH-siv)
    Autosomal recessive inheritance refers to genetic conditions that occur only when mutations are present in both copies of a given gene (i.e., the person is homozygous for a mutation, or carries two different mutations of the same gene, a state referred to as compound heterozygosity).