A condition is known to be "X-linked dominant". An affected man and an unaffected woman have a son. What is the likelihood that the son will be affected?
Correct answer: D. The son cannot be affected.
- A. There is a one in four chance the son will be affected.
- B. There is a three in four chance that the son will be affected.
- C. There is a one in two chance that the son will be affected.
- D. The son cannot be affected.
Explanation
A man passes his Y chromosome to his son. As the disease is X dominant, an affected father will not pass the disease to his son. Hence, option D is correct.
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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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