Unit of inherited material, encoded by a strand of DNA and transcribed by RNA. In higher organisms, genes are located on the chromosomes. A gene consistently affects a particular character in an individual —for example, the gene for eye color. Also termed a Mendelian gene, after Austrian biologist Gregor Mendel, it occurs at a particular point, or locus, on a particular chromosome and may have several variants, or alleles, each specifying a particular form of that character—for example, the alleles for blue or brown eyes. Some alleles show dominance. These mask the effect of other alleles known as recessive.
In the 1940s, it was established that a gene could be identified with a particular length of DNA, which coded for a complete protein molecule, leading to the “one gene, one enzyme” principle. Later it was realized that proteins can be made up of several polypeptide chains, each with a separate gene, so this principle was modified to “one gene, one polypeptide”. However, the fundamental idea remains the same, that genes produce their visible effects simply by coding for proteins; they control the structure of those proteins via the genetic code, as well as the amounts produced and the timing of production.
In modern genetics, the gene is identified either with the cistron (a set of codons that determines a complete polypeptide) or with the unit of selection (a Mendelian gene that determines a particular character in the organism on which natural selection can act). Genes undergo mutation and recombination to produce the variation on which natural selection operates.
The term “gene” was coined 1909 by the Danish geneticist Wilhelm Johannsen (1857–1927).
A self-replicating protein molecule that occupies a fixed place on a chromosome; a unit of heredity. + prikaži više