A test performed prior to conception to determine whether or not a couple are carriers of certain mutations in order to minimize the risk of transmitting diseases to their offspring.

If both partners have the same mutation in the same gene, there is a high risk of having children with health problems. The probability in this case would be that 50 % of the offspring will carry the mutation, 25 % will be healthy and 25 % will be sick.

The diseases that arise from this type of genetic combinations are potentially serious pathologies. Example Cystic fibrosis.