A woman is a carrier for a sex linked disorder. She marries a man whose father had the disorder, and whose mother did not. The man is unaffected. If they have a child, what is the probability that the child is also a carrier?
Correct answer: A. 25%
- A. 25%
- B. 50%
- C. 75%
- D. 1%
Explanation
The correct answer is 25%. Carriers are heterozygotes. In the case of recessive inheritance, a carrier will not know that they are carrying a single allele for the disease. In the Punnett Square, crossing two heterozygotes will result in 25% homozygous dominant and 50%heterozygous carriers, with 25% homozygous recessive who will have the disease.
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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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