How Many Mice Can Be Expected to Be Heterozygous for Both Fur and Eye Color?

Question:

Out of 64 offspring, how many mice can be expected to be heterozygous for both fur and eye color? Select one: a. 16 b. 12 c. 36 d. 1 e. 48 f. 4

Answer:

To solve this problem, we need to first determine the genotypes of the parent mice and then use a Punnett square to predict the genotypes and phenotypes of their offspring. The male mouse with black fur and black eyes is WWRR (homozygous dominant for both traits) and the female mouse with white fur and red eyes is wwrr (homozygous recessive for both traits). When these two mice mate, their offspring will all be WwRr (heterozygous for both traits) because each parent can only pass on one allele for each gene.

Out of the 64 offspring, we know that 30 had black fur and black eyes (WWRR or WWRr), and 34 had white fur and red eyes (wwrr). This means that the remaining offspring (64 - 30 - 34 = 0) must have had black fur and red eyes (Wwrr). When the heterozygous male (WwRr) mates with the heterozygous female (WwRr), we can use a Punnett square to predict the genotypes and phenotypes of their offspring:

| | W | w |

|---|---|---|

| R | WWRR | WWRr |

| r | WwRR | WwRr |

So, out of the 64 offspring, we can expect 16 (25%) to be heterozygous for both fur and eye color (WwRr). Therefore, the answer is a. 16.