What is the significance of a carrier in genetics?

The significance of a carrier in genetics is that it refers to an individual who possesses one copy of a recessive allele for a particular trait but does not express the trait themselves, as their other allele is dominant. Carriers play a crucial role in the inheritance of genetic conditions; they can pass the recessive allele to their offspring, potentially leading to the expression of the trait in the next generation if the offspring also inherit a recessive allele from the other parent.

For instance, in the case of autosomal recessive disorders like cystic fibrosis, a carrier will not exhibit symptoms of the disease but has a 50% chance of passing the recessive allele to each child. If the child inherits the recessive allele from both parents (if both are carriers), they will express the disease. Understanding the role of carriers helps in predicting the probability of genetic conditions manifesting in individuals and can inform decisions in genetic counseling.