Question

Your professor (Sam) and his wife (Becca) both have normal color vision, but their son is colorblind. What do you know about Sam's and Becca's genotypes?

A. Sam = c+c+ Becca = c+c+
B. Sam = c+c Becca = c+c
C. Sam=cY Becca=cc
D. Sam = c+Y Becca = c+c

Answer 1

D. Sam = c+Y Becca = c+c

Step-by-step explanation:

Colorblindness is a X-linked trait. Since Sam is a male and not colorblind, there's only one possible genotype he could have which is:

`Sam:\ X^(c+)Y`

Being c+ the dominant allele for not being colorblind while c is the recessive allele associated with colorblindness.

As for Becca, in order for her to not have colorblindness but her son do, she needs to have a heterozygous genotype and pass down the recessive Y allele to her son. Becca's genotype is:

`Becca:\ X^(c+)X^(c)`

Therefore, the answer is D. Sam = c+Y Becca = c+c