Question

individuals with the recessive phenotype are shaded darker than those with the dominant phenotype. if this trait is represented by the letter r, what is the genotype of individual r? rr rr rr rr or rr

Explanation:

Step1: Analyze the inheritance pattern

Since it is an autosomal trait and shaded individuals (like I) have the recessive phenotype (genotype \(rr\)). Parents \(C\) and \(D\) have a recessive - phenotype child (\(I\)). So \(C\) and \(D\) must be heterozygous (\(Rr\)) as they can pass on the recessive allele.

Step2: Determine the genotype of \(D\)

Individual \(D\) has a child with recessive phenotype (\(I: rr\)). Using the Punnett square for \(C (Rr)\times D (Rr)\):

Gametes of \(C\)	Gametes of \(D\)
\(r\)	\(Rr\)	\(rr\)

Since \(D\) has a recessive - phenotype child, and the trait is autosomal, and non - shaded individuals can be \(RR\) or \(Rr\). But when considering the cross that produced a recessive offspring, \(D\) must be able to pass on the recessive allele. However, if we assume \(A\) and \(B\) (parents of \(D\) and \(E\)): \(E\) is \(rr\) (shaded). So \(A\) and \(B\) must be \(Rr\) (because they have a recessive - phenotype child \(E\)). Then \(D\) (non - shaded) can be \(RR\) or \(Rr\)

Answer:

\(RR\) or \(Rr\)