Gene

Section on the DNA of a chromosome or the DNA present in mitochondria, plastids and plasmids that codes for certain hereditary structures or functions of an organism. The gene thus represents the smallest functional unit in the genome of an organism. I.d.R. each gene occupies a specific location on the chromosome, which is called gene locus or gene locus. However, there are also examples of genes consisting of several regions distributed on a chromosome. For example, genes coding for antibodies are assembled into a functional unit only as the cell differentiates.

Genes that occupy corresponding gene loci on homologous chromosomes are called allelic genes (short, but incorrectly "alleles"). They can be completely identical with regard to their genetic information. In this case the gene locus is called homozygous. But they can also be different from each other. In this case, the gene locus for the allele pair in question is called heterozygous. If a state form of a gene, i.e. an allele, overlaps the state form of another allele in its expression of a trait, this is called a dominant versus a recessive allele.

The totality of the genes of an organism in their respective identical or different state forms is called the genotype or genotype. A genetic map represents the linear arrangement of genes in the genome of an organism. Numerous genodermatoses have now been mapped (assigned on a gene map) and elucidated by molecular biology.