Null allele

A mutation that results in either no gene product or the absence of function at the phenotypic level.

Aneuploidy

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). (NCI Thesaurus)

Autosomal

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

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

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).

Positive predictive value

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

PPV

Positive predictive value. 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. (NCI Thesaurus)

NPV

Negative predictive value. 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. (NCI Thesaurus)

Negative predictive value

NPV. 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. (NCI Thesaurus)

Risk assessment

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.

Loss of heterozygosity

LOH. 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. (NCI Thesaurus)

Genetic susceptibility

Increased likelihood or chance of developing a particular disease due to the presence of one or more gene mutations and/or a family history that indicates an increased risk of the disease. Also called genetic predisposition. (NCI Thesaurus)

Genetic predisposition

Increased likelihood or chance of developing a particular disease due to the presence of one or more gene mutations and/or a family history that indicates an increased risk of the disease. Also called genetic susceptibility. (NCI Thesaurus)

Deoxyribonucleic acid

DNA. The molecular basis of heredity; encodes the genetic information responsible for the development and function of an organism and allows for transmission of that genetic information from one generation to the next. The DNA molecule is structured as 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. (NCI Thesaurus)

Exon

The sequence of DNA present in mature messenger RNA, some of which encodes the amino acids of a protein. Most genes have multiple exons with introns between them. (NCI Thesaurus)