Regarding color blindness when a normal male marries a carrier female, which is the correct statement?
Correct answer: D. Half of the sons will be color blind
- A. All daughters will be color blind
- B. All daughters will be carriers
- C. All sons will be color blind
- D. Half of the sons will be color blind
Explanation
In this genetic scenario, the mother is a carrier of the color blindness allele, with a genotype of XhX, and the father is normal with a genotype of XY. Daughters inherit one X chromosome from each parent, meaning they will receive a normal X chromosome from the father and either a carrier or a normal X chromosome from the mother. Thus, daughters cannot be color blind unless both parents pass on the color blindness allele, which is not possible here. Sons inherit the Y chromosome from the father and one X chromosome from the mother. Since the mother is a carrier, there is a 50% chance that sons will inherit the X chromosome with the color blindness allele, leading to half of the sons being color blind. The remaining sons will inherit the normal X chromosome and will not be color blind. Therefore, Option D is correct.
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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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