Recessive allele

A recessive allele is an allele that will not determine the phenotype unless the genotype is homozygous with that allele. Examples of recessive alleles include the allele for green in the pea Pisum sativum (the subject of Gregor Mendel's heredity experiments). In humans, a variety of inherited diseases are recessive, such as Cystic fibrosis and Tay-Sachs.