Here's why:
* Allele: A variant form of a gene.
* Carrier: An individual who carries one copy of a recessive allele for a trait but does not express the trait themselves.
For example, in the case of cystic fibrosis, an individual with one copy of the normal allele and one copy of the cystic fibrosis allele would be a carrier. They would not have cystic fibrosis themselves but could pass the recessive allele on to their offspring.
