Question

a dihybrid cross is created from plants that are heterozygous for both round seeds and yellow seed color. what is the ratio of offspring that have round seeds and yellow seed color?
1:16
3:16
9:16
16:16

Explanation:

Step1: Recall Dihybrid Cross Ratios

In a dihybrid cross of two heterozygous individuals (e.g., \( RrYy \times RrYy \), where \( R \) = round, \( r \) = wrinkled, \( Y \) = yellow, \( y \) = green), the phenotypic ratio of the offspring is \( 9:3:3:1 \) for the four possible phenotypes (round - yellow, round - green, wrinkled - yellow, wrinkled - green).

Step2: Identify the Desired Phenotype

The question asks for the ratio of offspring with round seeds (dominant, \( R\_ \)) and yellow seed color (dominant, \( Y\_ \)). From the \( 9:3:3:1 \) ratio, the number of offspring with both dominant traits (round and yellow) is 9 out of a total of \( 9 + 3+3 + 1=16 \) offspring. So the ratio is \( 9:16 \).

Answer:

C. 9:16