Red/green color blindness is due to mutations in opsin genes on the X chromosome

Question

Red/green color blindness is due to mutations in opsin genes on the X chromosome. The red or green opsin genes code for red or green opsin protein, which is a component of the red or green rhodopsins of red or green cones in the retina. Mutations in one of these genes, for example the red opsin gene, result in loss of ability to see red. Suppose a man who has red color blindness has children with a woman who is homozygous for the normal allele. What are the expected genotypes and phenotypes of their children? Are any of the children carriers? For full credit you need to use the correct notation for sex-linked traits.

Explanation / Answer

Let the allele for red opsin be Xr and the allele for green opsin be Xg.

The man with red color blindness will have the genotype XrY. This man is married to a normal female who is homozygous for the normal allele. The genotype of the female will be XX.

The cross becomes: XrY crossed to XX

Expected genotypes and phenotypes:

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