Principles of Genetics and Breeding

2.1.17 Carriers

• Recessive alleles (such as the one for albinism) are often deleterious to those who possess them in duplicate (homozygous recessive genotype).
• A heterozygote may appear just as normal as the homozygous dominant genotype.
• A heterozygous individual which possess a deleterious recessive allele hidden from phenotypic expression by the dominant normal allele is called a carrier.
• Most of the deleterious alleles harboured by a population are found in carrier individuals.