3. A B C D Your summer job is breeding mice for a scientist at the University of

Question

3. A B C D Your summer job is breeding mice for a scientist at the University of Chicago. You are given two true-breeding mice. One is white, has pink eyes, a long tail, thick fur, a strong immune system, and lacks whiskers. The other is black, has brown eyes, a short tail, thin fur, a weak immune system, and 23 pairs of whiskers. Your supervisor tells you that these traits are located on separate chromosomes. In the F1, all mice appear black, with brown eyes, short tails, thin fur, strong immune systems, and have 23 pairs of whiskers. In the F2, all possible combinations of these traits were expressed in ratios consistent with Mendelian inheritance. a. Which generation gives you the data to determine which allele is dominant for each trait? b. Fill in the table with the phenotype of the dominant and recessive allele for each trait: c. In the F2 generation, which phenotype appears most frequently? Show the expected frequency of this phenotype in the F2 using fractions. d. Which F2 phenotype appears least frequently? Show the expected frequency of this phenotype in the F2 using fractions. e. If the F1 generation was test-crossed (mated to mice with all recessive traits), how many different phenotypes would be produced?

Explanation / Answer

1. F1 generation will determine which is dominant and which is recessive allele

2.

e. If the F1 is testcrossed then the F1 will produce 64 gamates. The formla for number of gamates = 2n ; where n is number of heterozygous genes.

The recessive individual will produce 2 gamates of same type . The number of offspring phenotypes include 64

Trait Dominant recessive Coat color black white Eye color brown pink Tail length short tails long tails Fur thin fur thick fur Immune system strong immune system weak immune system Whiskers 23 pairs lack whiskers

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