A geneticist is studying two traits in corn: kernel color and kernel appearance or ‘shine'. The R/r alleles determine kernel color (R – purple color; r – yellow color). The W/w alleles determine kernel ‘shine' (W – waxy; w – dull). The geneticist crosses two corn plants that are Rr Ww and Rr ww . What phenotypic ratio is expected from these two parents?

Purple, waxy (R_W_) = 6

Purple, dull (R_ww) = 6

Yellow, waxy (rrW_) = 2

Yellow, dull (rrww) = 2

Phenotypic ratio = 3 (purple, waxy) :3 (purple dull) :1 (yellow waxy) :1 (yellow dull)

Explanation:

This question involves two genes coding for kernel color and kernel appearance or ‘shine in corn plants. The alleles for purple kernel (R) and kernel waxy (W) are dominant over the alleles of yellow color (r) and kernel dull (w).

According to this question, a geneticist cross two corn plants that have the genotype: RrWw and Rrww. The following gametes will be produced by each parent:

RrWw - RW, Rw, rW, and rw

Rrww - Rw, Rw, rw, and rw

Using these gametes in a punnet square (see attached image), the following proportion of offsprings will be produced:

Purple, waxy (R_W_) = 6

Purple, dull (R_ww) = 6

Yellow, waxy (rrW_) = 2

Yellow, dull (rrww) = 2

The phenotypic ratio expected from crossing these two parents is 3 (purple, waxy) :3 (purple dull) :1 (yellow waxy) :1 (yellow dull).

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