Sex-Linked Inheritance Problem Set

Problem 7: Red-green color blindness in humans

Tutorial to help answer the question

A human female "carrier" who is heterozygous for the recessive, sex-linked trait causing red-green color blindness (or alternatively, hemophilia), marries a normal male. What proportion of their male progeny will have red-green color blindness (or alternatively, will be hemophiliac)?

Tutorial

Genotypes and phenotypes of parents

The eggs of the mother will contain either a normal X chromosome or an X chromosome with the mutation causing red-green color blindness.

The sperm of the father will contain either the normal X chromosome or the Y chromosome.

Genotypes and phenotypes of offspring

None of the female children would be red-green color blind, but half would be "carriers."

Half of the sons would inherit the allele from their mother and be afflicted.

For help on setting up and interpreting a punnet square review the tutorial of problem 1 in Monohybrid Cross of Mendelian Genetics.

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Updated: July 15, 1999
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