Question

Round (R) is dominant over wrinkled (r) andGreen (Y) is dominant over (y) yellow. Cross thefollowing and express the phenotypic andgenotypic ratios. RrYy and rrYyA 12/16B 9/16C4/16D3/16

Answer 1

In this case, we have a dihybrid cross that is to say we are working with two alleles, the parental phenotype is round green (RrYy) and wrinkled green (rrYy). To obtain de genotypic ratios we must do the cross in a punnet square as follows.

We have the following genotypes and phenotypes

Round green, RrYY:2

Round green, RrYy:4

Round yellow, Rryy:2

Wrinkle green, rrYY:2

Wrinkle green, rrYy:4

Wrinkle yellow, rryy:2

Now the genotypic ratios of genotypes RrYy and rrYy are 4:16 (Option C 4/16), this is four of the 16 possible gametes will have RrYy combination and four of the 16 possible genotypes will have rrYy combination.

Now the phenotypic ratios are not considered in the options bus the logic is similar it would be 6:16, that is to say, six of the 16 possible offspring will have Round green phenotype, and 6 of the 16 will have Wrinkle green phenotype.