tRNA
Transfer RNA; and RNA molecule that transfers an amino acid to a growing polypeptide chain during translation.

Truncate
The premature termination of a protein product.

Tuberculosis
An infection of the lungs, accompanied by fever and a loss of appetite, caused by the bacillus Mycobacterium tuberculosis.

Turner Syndrome
A genetic condition in which an individual is XO (i.e. has only one sex chromosome, an X). Such individuals are phenotypically female, but are sterile because of undeveloped ovaries.

Two Hit Hypothesis (Knudson’s model)
Hypothesis that malignant transformation of cells occurs after at least two cellular mutation events or the “two hit theory”.

Typology
(1) The definition of classificatory groups by phonetic similarity to a “type” specimen. A species, for example, might be defined as all individuals less than x phonetic units from the species’ type. (2) The theory that distinct “types” exist in nature, perhaps because they are part of some plan of nature. (see also idealism.) The type of the species is then the most important form of it, and variants around that type are noise, or “mistakes.” Neo Darwinism opposes typology because in a gene pool no one variant is any more important than any others.