Carrier - GCSE Biology Definition

A carrier is an individual who has one copy of a recessive allele for a genetic trait or disorder but does not show any symptoms of the condition. This is because the dominant allele masks the effect of the recessive one. Although carriers are healthy, they can pass the recessive allele to their children. If two carriers have a child, there is a 25% chance the child will inherit both recessive alleles and have the disorder. Understanding carriers is important for predicting patterns of inheritance in genetic diagrams such as Punnett squares in GCSE Biology.