Allele

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

Variations in the base sequence of the DNA result in different forms of expression (alleles) of genes. These can change the phenotype. A gene, on the other hand, is a section of DNA that contains hereditary information for a specific trait. 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. The mutated form of the gene is called wild type. Mutated alleles are usually given a different name to distinguish them from the wild-type allele. How exactly this trait is expressed, i.e. in what way, is determined by the allele. For example, one allele can lead to blond hair and another to black hair.

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 alleles in a locus do not differ, the organism is homozygous.