Question

cystic fibrosis is a genetic disorder. it is a recessive trait that is determined by two alleles. suppose two parent carry at least one recessive allele, but neither of them has cystic fibrosis. which statement reflects the likelihod 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. the child may or may not have the disease because the disease does not depend on the alleles of the

Explanation:

Cystic fibrosis is a recessive disorder. Let the dominant allele be \(A\) and the recessive allele be \(a\). Since neither parent has the disease but both carry at least one recessive allele, their genotypes are \(Aa\). When they have a child, the possible allele combinations for the child are \(AA:Aa : aa=1:2:1\) (from Punnett square analysis: \(Aa\times Aa\) gives \(AA\), \(Aa\), \(Aa\), \(aa\)). A child with \(aa\) will have cystic fibrosis, while those with \(AA\) or \(Aa\) will not. So, there is a chance (25% for \(aa\)) that the child may inherit two recessive alleles (\(aa\)) and have the disease, or inherit one or no recessive alleles (\(AA\) or \(Aa\)) and not have the disease.

Answer:

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