Punnett squares are a type of diagram that scientists use to predict the outcome of a breeding or cross experiment. Biologists use this method to figure out the probability of an offspring possessing a specific genotype.
Punnett squares can be helpful for parents and doctors who are trying to determine if a child will be born with a specific disease. If both parents are carriers for a disease like cystic fibrosis, for example, this type of diagram works to determine the probability of a child being born with that gene. It also helps to determine the probability of the child being a carrier.