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 with two heterozygous traits (e.g., RrYy × RrYy, where R = round, r = wrinkled; Y = yellow, y = green), the phenotypic ratio is \(9:3:3:1\) for dominant - dominant : dominant - recessive : recessive - dominant : recessive - recessive.

Step2: Identify the Desired Phenotype

We want round (dominant, R_) and yellow (dominant, Y_). From the \(9:3:3:1\) ratio, the number of offspring with both dominant traits (round and yellow) is 9 out of 16 total combinations. So the ratio of offspring with round seeds and yellow seed color is \(9:16\) (since the total number of possible genotypes from a dihybrid cross is 16, and 9 of them have both dominant phenotypes).

Answer:

9:16