NCI Dictionary of Genetics Terms

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Welcome to the NCI Dictionary of Genetics Terms, which contains technical definitions for more than 150 terms related to genetics. These definitions were developed by the PDQ® Cancer Genetics Editorial Board to support the evidence-based, peer-reviewed PDQ cancer genetics information summaries.

11 results found for: T
tagging SNP
(TA-ging snip)
A single nucleotide polymorphism, or SNP, that is used to “tag” a particular haplotype in a region of the genome. As a subset of all of the SNPs in the genome, tagging SNPs can be extremely useful for testing the association of a marker locus with a qualitative or quantitative trait locus in that it may not be necessary to genotype all of the SNPs. Also called tagSNP.
tagSNP
(tag-snip)
A single nucleotide polymorphism, or SNP, that is used to “tag” a particular haplotype in a region of the genome. As a subset of all of the SNPs in the genome, tagSNPs can be extremely useful for testing the association of a marker locus with a qualitative or quantitative trait locus in that it may not be necessary to genotype all of the SNPs. Also called tagging SNP.
throughput
(THROO-put)
The quantity of information, people, or materials that is put through a process in a specific period of time. In medicine, it can be used to describe the efficiency of laboratory procedures, such as genetic sequencing, or the number of patients seen in a clinic in a certain period of time.
transcription
(tran-SKRIP-shun)
The process of synthesizing messenger RNA (mRNA) from DNA.
translation
(trans-LAY-shun)
The process of synthesizing an amino acid sequence (protein product) from the messenger RNA code.
translocation
(TRANZ-loh-KAY-shun)
A type of chromosomal abnormality in which a chromosome breaks and a portion of it reattaches to a different chromosomal location.
trichilemmoma
(TRIH-kih-leh-MOH-muh)
A benign tumor arising from the outer cells of the hair follicle.
trinucleotide repeat
(try-NOO-klee-oh-tide reh-PEET)
Sequences of 3 nucleotides repeated in tandem on the same contiguous section of chromosome. A certain amount of normal (polymorphic) variation in repeat number with no clinical significance commonly occurs between individuals; however, repeat numbers over a certain threshold can, in some cases, lead to adverse effects on the function of the gene, resulting in genetic disease.
triple-negative breast cancer
(TRIH-pul-NEH-guh-tiv brest KAN-ser)
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.
trisomy
(TRY-soh-mee)
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).
tumor sequencing
(TOO-mer SEE-kwen-sing)
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.