Recessiveness (from the Latin recessus - deviation) is a type of inheritance of traits in which the recessive allele of a gene manifests itself in the phenotype of an organism only in a homozygous state, when the organism has two identical recessive alleles of the same gene.
If there are dominant and recessive alleles of the same gene in a heterozygous state, the recessive trait does not appear, since the dominant allele suppresses the effect of the recessive one. Recessive traits appear only in the absence of a dominant allele in the genotype.
Recessive inheritance is characteristic of many genetic diseases, such as phenylketonuria, cystic fibrosis, as well as some physical characteristics, such as blue eyes. Recessive genes also play an important role in the evolution of populations.