Question

EXPERIMENT 1: PUNNETT SQUARE CROSSES Part 1: Post-Lab Questions 1. Set up and complete Punnett squares for these crosses (remember Y = yellow, y = blue): a. YY and Yy b. YY and yy 2. Answer these questions: a. What are the resulting phenotypes? b. Are there any blue kernels? c. How can you tell whether or not there are blue kernels? 3. Set up and complete a Punnett square for a cross of two of the F1 from Step 1 (above). 4. Answer these questions: a. What are the genotypes of the F2 generation? b. What are their phenotypes? c. Are there more or fewer blue kernels than in the F1 generation? 5. Identify the four possible gametes produced by the following individuals (S = smooth, s = wrinkled): a. YY Ss: b. Yy Ss:

Answer 1

2. Answer: a. Resulting phenotypes: 100% Yellow.

                   b. No, there are not blue kernels.

                   c. All kernels are yellow because the yellow allele (Y) is    

                       dominant  over blue allele (y).

Explanation: Crosses a (YY x Yy) and b (YY x yy) result in yellow offspring with genotypes: 1) Dominant homozygote (YY) and 2) Heterozygous (Yy).

4. Answer: a. Genotypes: YY (25%) , Yy (50%) and yy (25%).

                  b. Phenotypes: Yellow  (75%) and blue (25%).

                  c. There are more blue kernels in the F2 than in the F1.

Explanation: Crosses between F1 members (Yy x Yy)  result in yellow and blue offspring with genotypes: 1) Dominant homozygote (YY, 25%)  2) Heterozygous (Yy, 50%) and 3) Recessive homozygote (yy, 25%).

5. Answer: a. Ys and YS

                   b. YS, yS, Ys, ys.

Explanation: The yellow and smooth individuals with genotype  (YYSs) can produce two different gametes: Ys (Yellow and wrinkled) and YS (Yellow and smooth). The yellow and smooth individuals with genotype  (YySs) can produce four different gametes: YS (yellow ans smooth), yS (Blue and smooth), Ys (Yellow and wrinkled) and ys (Blue and wrinkled).