Question

in tomatoes, red fruit (r) is dominant over yellow fruit (r). what is the probability that an offspring of plants that are heterozygous (rr) produce plants with the homozygous recessive (rr) genotype?
a. 0
b. $\frac{1}{4}$
c. $\frac{1}{2}$
d. $\frac{3}{4}$

Explanation:

Step1: Set up Punnett square

Parents: $Rr \times Rr$. Gametes: $R, r$ for each parent.

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

Step2: Count recessive genotype

Identify $rr$: 1 out of 4 total genotypes.

Step3: Calculate probability

Probability = $\frac{\text{Number of } rr}{\text{Total genotypes}} = \frac{1}{4}$

Answer:

B. 1/4