Updated by: Arabinda Naik
Recessive alleles are the allele that cannot express themselves in presence of the dominant allele. Only when two recessive alleles are present then only it can they express themselves. This means in homozygous conditions only; they can be expressed. In presence of a dominant allele, either phenotype of the dominant allele is expressed, or a different phenotype than both alleles will appear. This means in heterozygous conditions of alleles; recessive one cannot be expressed. The allele which can be expressed only when present in homozygous conditions are recessive alleles. Recessive alleles can be expressed only in homozygous conditions of any generation. For instance, alleles of blue eyes are recessive, hence for one to have blue eyes, two copies of the blue eye allele must be present.