LOD score

Logarithm of the odd score. 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 three or more is generally considered statistically significant evidence of linkage. Also called logarithm of the odd score. (NCI Thesaurus)

Logarithm of the odd score

LOD score. 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 three or more is generally considered statistically significant evidence of linkage. Also called LOD score. (NCI Thesaurus)

Intron

The sequence of DNA in between exons that is initially copied into RNA but is cut out of the final RNA transcript and therefore does not change the amino acid code. Some intronic sequences are known to affect gene expression. (NCI Thesaurus)

Presymptomatic testing

Genetic analysis of an asymptomatic or unaffected individual who is at risk of a specific genetic disorder.

Splicing

The process by which introns, the noncoding regions of genes, are excised out of the primary messenger RNA transcript, and the exons (i.e., coding regions) are joined together to generate mature messenger RNA. The latter serves as the template for synthesis of a specific protein. (NCI Thesaurus)

Linkage

The tendency for genes or segments of DNA closely positioned along a chromosome to segregate together at meiosis, and therefore be inherited together.

Variable expression

Variation in the manner in which a trait is manifested. When there is variable expressivity, the trait may vary in clinical expression from mild to severe. For example, the condition neurofibromatosis type 1 may be mild, presenting with café-au-lait spots only, or may be severe, presenting with neurofibromas and brain tumors.

SNP

Single nucleotide polymorphism. DNA sequence variations that occur when a single nucleotide (adenine, thymine, cytosine, or guanine) in the genome sequence is altered; usually present in at least 1% of the population; pronounced "snip". Also called single nucleotide polymorphism. (NCI Thesaurus)

Polymorphism

A common mutation. “Common” is typically defined as an allele frequency of at least 1%. All genes occur in pairs, except when x and y chromosomes are paired in males; thus a polymorphism with an allele frequency of 1% would be found in about 2% of the population, with most carriers having one copy of the polymorphism and one copy of the normal allele. (NCI Thesaurus)

Linkage analysis

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

Mutation analysis

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

Trisomy

The presence of an extra chromosome, resulting in a total of three copies of that chromosome instead of the normal 2 copies (e.g., trisomy 21, or Down syndrome). (NCI Thesaurus)

Translation

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

Nutrigenomics

The study of the interaction of dietary and genetic factors and its effect on metabolism, health status, and risk of disease.

SSCP

A laboratory test used to separate single-stranded nucleic acids based on subtle differences in their DNA sequence, often a single base pair, which results in a different secondary structure and a measurable difference in mobility through a gel. Also called single-stranded conformation polymorphism analysis. (NCI Thesaurus)