Allele

An allele (from Greek allélon "one another, mutual") refers to a possible expression of a respective hereditary factor (gene), which is located at a specific place (locus) on a chromosome.

Variations in the base sequence of the DNA give rise to different forms of expression (alleles) of genes. These can change the phenotype. However, more than two different state forms of a gene can also occur, i.e. > two alleles occur at one gene locus (multiple alleles). Alleles are also those expressions of genes that contain mutations that cause, for example, loss of function of the gene. These alleles are usually given a different name to distinguish them from the wild-type allele.

A single allele is inherited from one parent at a time. If the alleles differ in one locus, the organism is heterozygous. The dominant hereditary trait prevails. If the allelesin a locus do not differ, the organism is homozygous .