Question

9. The probability that a boy whose mother is heterozygous for a sex-linked trait having the trait is:

10. The probability that the daughter of a mom with a dominant disease-causing allele on the X chromosome and a dad with the disorder will be affected with the disorder is:



11. An unaffected man and an unaffected woman have a son with Lesch-Nyhan syndrome, an X-linked recessive trait. What are the chances that a daughter of this couple will inherit Lesch-Nyhan syndrome?



12. A man has the X-linked dominant condition CGH that produces dense hair on the face and upper body. What is the chance that he will pass it on to his daughters?

Answer 1

Step-by-step explanation:

The probability that the daughter of a mom with a dominant disease-causing allele on the X chromosome and a dad with the disorder will be affected with the disorder is 100%. This is because the daughter will inherit one X chromosome from the mom, which carries the dominant allele that causes the disorder, and one X chromosome from the dad, which is affected by the disorder.

Since the parents are unaffected, we can infer that they are both heterozygous carriers of the Lesch-Nyhan syndrome allele. If they have a son with the syndrome, we know that the son inherited the recessive allele from both parents. The chance that a daughter of this couple will inherit Lesch-Nyhan syndrome is 25%. This is because the daughter will inherit one X chromosome from the father, which does not carry the recessive allele, and one X chromosome from the mother, which has a 50% chance of carrying the recessive allele.

Since the condition is X-linked dominant, the man will pass on the dominant allele to all of his daughters. Therefore, the chance that he will pass it on to his daughters is 100%.