n. a group of closely linked genes that regulate the production of enzymes in bacteria. An operon is composed of one or more structural genes, which determine the nature of the enzymes made, and operator and promoter genes, which control the working of the structural genes. The operator is itself controlled by a regulator gene, which is not part of the operon.
n. the basic unit of genetic material, which is carried at a particular place on a *chromosome. Originally it was regarded as the unit of inheritance and mutation but is now usually defined as a sequence of *DNA or *RNA that acts as the unit controlling the formation of a single polypeptide chain (see cistron). In diploid organisms, including humans, genes occur as pairs of *alleles. Various kinds of gene have been discovered: structural genes determine the biochemical makeup of the proteins; regulator genes control the rate of protein production (see operon). Architectural genes are responsible for the integration of the protein into the structure of the cell, and temporal genes control the time and place of action of the other genes and largely control the *differentiation of the cells and tissues of the body.... gene
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