Carrier

A carrier is an organism that carries a disease without showing any signs or symptoms. If the disease is genetic, the carrier will be heterozygous, with a dominant, healthy allele and a reccessive allele for the disease state. In the event of two carriers mating, there is a 25% chance their offspring will be affected by the disease, 50% chance of the offspring being carriers too or a 25% chance of the offspring being healthy and not a carrier.

An example of this is Cystic Fibrosis, where 1 in 25 of the white population are carriers of the CF gene, showing no signs of having CF themselves.

A Punnett Square showing two carriers mating: (H is healthy, dominant allele, h is recessive for disease state)

	H	h
H	HH	Hh
h	Hh	hh