Color Blindness Problem Set

Problem 3: Barbara's genotype

We have determined that Audrei is homozygous recessive for the red-green color blind allele and that her father is hemizygous with a recessive allele. What is the mother's genotype? Remember that Audrei's mother does not have a color perception defect.

You answered: A. homozygous for the dominant, normal vision allele
If Barbara, the mother, were homozygous for the dominant, normal vision allele, she would have normal vision and her daughter Audrei would be "carrier", but would have normal vision.
Female Genotype Female Phenotype
XR XR Normal Vision
XR Xr Normal vision, "carrier"
Xr Xr Red-green color blind

The Biology Project
University of Arizona
Saturday, October 10, 1998
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