Topanga’s mother has blue eyes and her father has brown eyes. The allele for brown eye color is dominant (B) to the allele for blue eye color (b), but Topanga has blue eyes. Therefore, Topanga’s must be and her father’s must be Bb. a. genotype; bb
b. phenotype; Bb
c. genotype; Bb
d. phenotype; bb

a. genotype; bb

Explanation:

Given that;

The allele for brown eye color is dominant (B)  to the allele for blue eye color (b)

and Topanga’s mother has blue eyes

Definitely the traits of Topanga’s mother is recessive for blue traits = bb

Her father has brown eyes = Bb (since B is dominant over b) therefore, the b allele is not expressed.

So if Bb crosses with bb; we have:

                         B                      b

b                      Bb                      bb

b                      Bb                      bb

∴ Since Topanga has blue eyes, it is expressed by the genotype bb because bb is a recessive genotype expressing the blue eye color.