Sex-Linked Inheritance Problem Set

Problem 4: Predicting genotype when phenotype is known

Tutorial to help answer the question

What is the genotype of a red-eyed, yellow-bodied female fruit fly who is homozygous for the eye color allele?
Red eyes (w+) and tan bodies (y+) are the dominant alleles. (Both traits are X chromosome linked).


Possible female genotypes

Since the female fly has a yellow body, and the tan body color is the dominant allele, she will be homozygous recessive for yellow body color.

Therefore, the female fly will be homozygous for both traits.

The genotype is Xw+y Xw+y.

The Biology Project
University of Arizona
Updated: July 15, 1999
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