Question

the illustration below shows two adult rabbits and their offspring.

in rabbits, the allele for spots is dominant to the allele for solid color. what is the most likely genotype of the parent rabbits in the illustration?

• rr x rr
• rr x rr
• rr x rr
• rr x rr

Explanation:

Step1: Analyze the offspring phenotypes

Since the allele for spots (let's assume \(R\)) is dominant over solid - color (\(r\)). The parents have offspring with both spot and solid - color phenotypes. If one parent was \(RR\), all offspring would have spots (because \(RR\times\) any genotype would give at least one \(R\) allele). So the parents cannot be \(RR\times\) any genotype.

Step2: Consider the cross \(Rr\times Rr\)

Using the Punnett square for \(Rr\times Rr\):

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The genotypic ratio is \(RR:Rr:rr = 1:2:1\), and the phenotypic ratio (assuming \(R\) is dominant) is \(3\) (spotted) \(:1\) (solid - colored). This cross can produce both spotted (\(RR\) or \(Rr\)) and solid - colored (\(rr\)) offspring.

Step3: Consider \(Rr\times rr\)

Using the Punnett square for \(Rr\times rr\):

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The genotypic ratio is \(Rr:rr=1:1\), and the phenotypic ratio is \(1\) (spotted) \(:1\) (solid - colored). But if we assume a relatively large number of offspring (as in the illustration), the \(Rr\times Rr\) cross is more likely to produce a variety of offspring in a non - \(1:1\) phenotypic ratio for dominant and recessive traits (since in the illustration, there are more than two offspring).

Step4: Consider \(rr\times rr\)

If both parents were \(rr\), all offspring would be solid - colored (\(rr\))

Answer:

\(Rr\times Rr\)