AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

MULTIPLE ALLELES

• In all diploid organisms, in each somatic cell there are two homologous chromosomes.
• Each one of these homologous chromosomes carries one allele of a gene at a particular locus. So there are two alleles in a locus of each cell of an individual.
• When more than two alternative alleles are present for a gene, they are called multiple alleles.
• In these cases two or more different mutations must have taken place at the same locus but in different individuals or at different times.
• A capital letter symbol is used to designate allele which is dominant to all other alleles for that specific gene.
• Corresponding small letter is used to designate allele which is recessive to all other alleles for that specific gene.
• Other intermediate alleles are designated with same letter with some suitable subscript based on their degree of dominance between the two extreme alleles.