Question

practice 2
in mendels garden peas, round peas (r) are dominant to wrinkled peas (r). for each cross given in the chart below, indicate the possible genotypes and phenotypes. you may select one circle or multiple circles in each row to indicate the possible genotypes and phonotypes. select all that apply.

1. two heterozygous round pea plants
2. a homozygous round pea plant and a homozygous wrinkled pea plant
3. a heterozygous round pea plant and a homozygous wrinkled pea plant

Explanation:

Step1: Analyze Cross 1 (Rr × Rr)

Using Punnett square:

$$\begin{array}{|c|c|c|} \hline & R & r \\ \hline R & RR & Rr \\ \hline r & Rr & rr \\ \hline \end{array}$$

Genotypes: \(RR\) (25%), \(Rr\) (50%), \(rr\) (25%). Phenotypes: round (\(RR + Rr=75\%\)), wrinkled (\(rr = 25\%\)). So for Cross 1: \(RR\) (A), \(rr\) (B), \(Rr\) (C), round (D), wrinkled (E).

Step2: Analyze Cross 2 (RR × rr)

Using Punnett square:

$$\begin{array}{|c|c|c|} \hline & R & R \\ \hline r & Rr & Rr \\ \hline r & Rr & Rr \\ \hline \end{array}$$

Genotype: \(Rr\) (100%). Phenotype: round (100%). So for Cross 2: \(Rr\) (C), round (D).

Step3: Analyze Cross 3 (Rr × rr)

Using Punnett square:

$$\begin{array}{|c|c|c|} \hline & R & r \\ \hline r & Rr & rr \\ \hline r & Rr & rr \\ \hline \end{array}$$

Genotypes: \(Rr\) (50%), \(rr\) (50%). Phenotypes: round (\(Rr = 50\%\)), wrinkled (\(rr=50\%\)). So for Cross 3: \(rr\) (B), \(Rr\) (C), round (D), wrinkled (E).

Answer:

1. A. \(RR\), B. \(rr\), C. \(Rr\), D. round, E. wrinkled
2. C. \(Rr\), D. round
3. B. \(rr\), C. \(Rr\), D. round, E. wrinkled