Red-green colour blindness is a sex-linked recessive trait. If a colour-blind man marries a woman with normal vision whose father is colourblind and they have a daughter, what is the probability that she will be colourblind?
Correct answer: C. 0.50
- A. 0
- B. 0.25
- C. 0.50
- D. 0.75
Explanation
The woman had a color-blind father. He was, therefore: XcY. Herself, she has normal vision, meaning she is X+X. She certainly didn't inherit the X+ from her dad! Yet her dad must have given her something!! We conclude she got the Xc from her father and that she is X+Xc. Our problem is half solved. Her husband is colorblind. Since he is hemizygous, his genotype must be: XcY Okay, let's look at the children this couple can produce from the image attached. XcY x X+Xc.Out of all the children, we have a 50% or 0.50 chance that she will be color-blind. (NOTE: Extra Point ---->Out of all the daughters, we have a 50% chance that she will be color-blind)
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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