Question

cystic fibrosis is a genetic disorder. it is a recessive trait that is determined by two alleles. suppose two parents each carry at least one recessive allele, but neither of them has cystic fibrosis. which statement reflects the likelihood of a child of these parents having cystic fibrosis?

the child cannot have the disease because only the dominant alleles will be passed on
the child will have the disease because only recessive alleles will be passed on
the child may or may not have the disease because a recessive gene from each parent may be passed on
the child may or may not have the disease because the disease does not depend on the alleles of the parents

Explanation:

Cystic fibrosis is recessive, so parents (carriers, heterozygous) can pass recessive alleles. A child gets one allele from each parent. If both pass recessive, the child has the disease; else, not. So the child may or may not have it as recessive genes from each parent could be passed. Other options are wrong: dominant isn't the only one passed, recessive isn't the only one, and the disease does depend on parents' alleles.

Answer:

The child may or may not have the disease because a recessive gene from each parent may be passed on.