A woman with normal vision, but whose father was color blind, marries a color blind man. Suppose that the fourth child of this couple was a boy. This boy:
Correct answer: A. May be colour blind or may be of normal vision
- A. May be colour blind or may be of normal vision
- B. Must be colour blind
- C. Must have normal colour vision
- D. Will be partially colour blind since he is heterozygous for the colour blind mutant allele
Explanation
The correct answer is that the boy's vision is uncertain. He may either be color blind or have normal vision, as it depends on which allele he inherits from his mother. This situation is determined by the probabilistic nature of inheritance in X-linked recessive traits, where carriers (heterozygous individuals) have a 50% chance of passing on the mutant allele.
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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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