In the same mouse species, a fourth unlinked gene (gene P/p) also affects fur co
ID: 15354 • Letter: I
Question
In the same mouse species, a fourth unlinked gene (gene P/p) also affects fur color.For mice that are either homozygous dominant (PP) or heterozygous (Pp), the organism’s fur color is dictated by the other three genes (A/a, B/b, and C/c).
For mice that are homozygous recessive (pp), large patches of the organism’s fur are white. This condition is called piebaldism.
In a cross between two mice that are heterozygous for agouti, black, color, and piebaldism, what is the probability that offspring will have solid black fur along with large patches of white fur? (Hint: Consider each gene separately; then use the multiplication rule. For more help getting started, see Hint 1.)
Express your answer as a fraction using the slash symbol and no spaces (for example, 3/16).
Explanation / Answer
Because each gene segregates independently, you need to determine the probability of each genotype independently and then multiply the four probabilities together. The probability of offspring with solid color (aa) is 1/4; the probability of offspring with black fur (BBor Bb) is 3/4; the probability of colored fur (CCor Cc) is 3/4; and the probability of piebald, or white patches (pp), is 1/4. The combined probability is1/4 x 3/4 x 3/4 x 1/4 = 9/256.