Question

In rats, assume that spotted skin (S) is dominant over non-spotted skin (s) and that wooly hair (W) is dominant over non-wooly hair (w). Cross a heterozygous spotted, non wooly ear with a heterozygous wooly-haired, non-spotted rat

a. Give the parent genotypes _______x______
b. What is the probability that their offspring will have spotted skin and Wooly hair?_____

Answer 1

In a cross between a heterozygous spotted, non-wooly rat (Ssww) and a heterozygous wooly-haired, non-spotted rat (ssWw), the parent genotypes are Ssww x ssWw. Using a Punnett Square, we find that the probability of their offspring having both spotted skin and wooly hair is 12.5%.

Step-by-step explanation:

To answer the question of crossing a heterozygous spotted, non-wooly rat (SsWw) with a heterozygous wooly-haired, non-spotted rat (ssWw), we first need to identify the parent genotypes:

• Parent 1 genotype: Ssww (heterozygous spotted, non-wooly)
• Parent 2 genotype: ssWw (heterozygous wooly-haired, non-spotted)

Next, we use a Punnett Square to determine the probability of their offspring having spotted skin and wooly hair. We set up a dihybrid cross, combining each possible allele from one parent with each possible allele from the other. The phenotypic ratio for this dihybrid cross typically follows a 9:3:3:1 pattern, but since we are crossing Ssww with ssWw, we observe a different phenotypic ratio.

To determine the specific probability of offspring having spotted skin and wooly hair (SW), we need to find out how many of the 16 squares in the Punnett Square represent this phenotype. In this case, the probability of having offspring with both spotted skin (S) and wooly hair (W) is 2 in 16, or 12.5%.