After reading the paragraphs below, answer the questions that follow. Mr. and Mr

Question

After reading the paragraphs below, answer the questions that follow. Mr. and Mrs. Smith have three sons in elementary school. Two of their children are progressing normally, but their youngest son, Charles, has been much slower than his siblings in developing speech and language skills. His parents are concerned that he has a learning disability and decide to investigate further. Since some learning disabilities can be genetically based, their pediatrician recommends a chromosomal analysis. The results show that Charles has a trisomy of the sex chromosomes, diagnosed as XYY. A mistake during sperm formation resulted in an extra copy of the Y chromosome. The extra copy was passed on to Charles during fertilization Most often, this chromosomal change causes no unusual physical features or medical problems, but those with trisomy of the sex chromosomes may have a higher-than-normal risk of delays in learning development. The problem that occurred during meiosis in sperm formation was an inversion of the X chromosome, preventing the pairing of sex chromosomes. failure of the second meiotic division to take place. nondisjunction involving a Y chromosome. formation of diploid sperm.

Explanation / Answer

Nondisjuction involving a Y chromosome is correct answer.

In normal conditions, both the sex chromosomes of male and female get separated in the meiosis but in case of nondisjuction the chromosomes donot separate from each other.

Reason for XYY genotype is the nondisjuction of Y chromosome in meiosis 2. Y chromosome do not separate from each other resulting in sperm containing the two Y chromosomes. When this sperm fertilize an egg the zygote will have XYY genotype.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

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