32. X-Linked Genetic Disease Men have XY (or YX) chromosomes and women have XX c

Question

32. X-Linked Genetic Disease Men have XY (or YX) chromosomes and women have XX chromosomes. X-linked recessive genetic diseases (such as juvenile retinoschisis) occur when there is a defective X chromosome that occurs without a paired X chromosome that is not defective. In the following, represent a defective X chromosome with lowercase x, so a child with the xY or Yx pair of chromosomes will have the disease and a child with XX or XY or YX or xX or Xx will not have the disease. Each parent contributes one of the chromosomes to the child. is the probability that a son will inherit the disease? b. If a father has the defective x chromosome and the mother has good XX chromosomes, what is the probability that a daughter will inherit the disease? c. If a mother has one defective x chromosome and one good X chromosome and the father has good XY chromosomes, what is the probability that a son will inherit the disease? d. If a mother has one defective x chromosome and one good X chromosome and the father has good XY chromosomes, what is the probability that a daughter will inherit the disease?

Explanation / Answer

#Chegg policy states that in case of multiple questions, answe the first, so answering question 32

a) Given that son is a male, he will have XY type chromosome, so number of ways of getting the X chromosome

3 (1 from father and 2 from mother) and number of ways of getting Y chromosome - 1

So total sample space = 3

Probability that son will inherit the disease = no of ways getting the disease/total sample space = 1/3

b) Given that daughter will have XX type chromosome, her chromose types will be either xX, XX or Xx

All these won't lead to disease, so she won't inherit the disease

P(disease) = 0

c) P(son will inherit disease given Mother has defective chromosome) = 1/3

Only 1 way to get the disease and total sample space = 3

d) Similar to example b) the daughter will always have xX, XX or Xx type chromosome, so she will never inherit the disease

P(disease) = 0

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