Sex-limited Male-limited precocious puberty results from a rare, sex-limited aut

Question

Sex-limited Male-limited precocious puberty results from a rare, sex-limited autosomal allele (P) that is dominant over the allele for normal puberty (p) and is expressed only in males. Bill undergoes precocious puberty, but his brothe Jack and his sister Beth underwent puberty at the usual time, between the ages of 10 and 14. Although Bill's mother and father underwent normal puberty, two of his maternal uncles (his mother's brothers) underwent precocious puberty. All of Bil's grandparents underwent normal puberty. Give the most likely genotypes for the relatives mentioned in this family.

Explanation / Answer

Sex-limited traits are expressed only in a particular sex even if it can be present in other sex. Here since Bill shows precocious puberty he must be Pp, while his father must be pp because if even P was present heterozygously in his father Bill's brother would too have got the allele and he would show the same. So Bill's brother is pp. Bill must have received the P allele from his mother who must be Pp as well because Bill's brother is unaffected. Bill's sister could be Pp or pp But she is unaffected since the trait is sex-limited. Bill's maternal uncles must be Pp as well. The reason is since they are affected they must carry at least one P, not necessarily homozygously, so they can be PP or Pp.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

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