Suppose that a man and a woman, neither of whom are affected by the disease, hav

Question

Suppose that a man and a woman, neither of whom are affected by the disease, have a son with cystic fibrosis. What is the probability that their second child will be unaffected by the disease? Suppose that the man and woman from part (a) have an unaffected daughter. What is the probability that she carries a harmful copy of the cystic fibrosis gene, given that she is unaffected? Suppose that the daughter from part (b) marries a man with cystic fibrosis. If the couple has a child together, what is the probability that their child will be unaffected? Suppose that the couple from part (c) have an unaffected child. What is the probability that their second child will be unaffected, given that their first child was unaffected?

Explanation / Answer

cyctic fibrosis will happen if both the gene are recessive.

let r is recessive and d is dominant gene,

hence there are 4 possibilities of a progeny to have a fllowing composition of genes {rr,rd,dr,dd}

a) there is only one possible way to have cyctic fibrosis out of four {rr}

hence probability =1/4

b) as there are 3 possibilty to have cystic fibrosis allele and 2 out of them to remain unaffected

hence probability =2/3

c)probabilty that their child remain unaffected=she has cystic fibrosis allele and child remain unaffected+she does not carry allele and child remain unaffected =(3/4)*(3/4)+(1/4)*1=13/16

d)probabilty that first child was unaffected =9/16

probability that both child are unaffected =(3/4)*(3/4)(3/4)+(1/4)*1*!=43/64

hence probabilty that their second child will be unaffected, given first child was unaffected =(43/64)/(13/16)=0.8269

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.