The accompanying pedigree is for Huntington disease (HD), a late-onset disorder

Question

The accompanying pedigree is for Huntington disease (HD), a late-onset disorder of the nervous systèm. The slashes indicate deceased family members Is this pedigree compatible with the mode of inheritance for HD mentioned in the chapter? Consider the two newborn children in the two arms of the pedigree, Susan in the left arm and Alan in the right arm. Study the graph shown in lecture (march 11th) come up with an opinion on the likelihood that they will develop HD. Assume for the sake of the discussion that parents have children at age 25. 1. 100 0 10 20 30 40 50 60 70 80 Susan Alan Age (years) A rare, recessive allele inherited in a Mendelian manner causes the disease cystic fibrosis. A phenotypically normal man whose father had cystic fibrosis marries a phenotypically normal woman from outside the family, and the couple considers having a child. a) Draw the pedigree as far as described. b) If the frequency in the population of heterozygotes for cystic fibrosis is 1 in 50, what is the chance that 2. the couple's first child will have cystic fibrosis? If the first child does have cystic fibrosis, what is the probability that the second child will be normal? c)

Explanation / Answer

Ans1)

Yes, the pedigree is consistent

It is a autosomal dominant trait. In first generation,

The affected parent is Hh and unaffected is hh. Thus 50% of its progeny can be Aa (affected).

Likewise, III-3&4 are unaffected (hh) and thus none of the child in the lineage is affected thereafter.

Thus Susan and Alan have no likelihood of disease.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

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