Description
Alleles are variants in the DNA that occur at a specific position on the chromosome (locus). An allele is a single copy of a genetic letter or a whole gene, inherited from one parent. A person can be heterozygous (two different alleles) or homozygous (two identical alleles) for each specific position on a chromosome. This determines what feature will be expressed in a person, for example their hair color, body height or blood group.