Question

Consider the abbreviated model of meiosis and the four gametes produced at the completion of meiosis II. Imagine that these gametes represent four sperm. If sperm C. fertilizes a normal egg, what will be the result? A) Trisomy B) Trisomy X C) Trisomy 21 D) Down's syndrome

Answer 1

Answer:

A: Trisomy

Explanation:

Trisomy The result of fertilization of sperm C with a normal egg containing the haploid chromosome number would be trisomy. We do not know what chromosome underwent nondisjunction, so we cannot be more specific.

Answer 2

The right answer is A) Trisomy

Aberrant karyotypes containing an abnormal number of chromosomes are known in the human species. The best-known (and most common) chromosomal abnormality is trisomy 21, which is responsible for Down syndrome (mongolism). There are others such as Turner syndrome (woman with a single X chromosome) or Klinefelter syndrome (man XXY).

These abnormalities originate from the non-disjunction of the chromosomes of a pair of homologues during metaphase I of meiosis. At the end of division I, a daughter cell contains the two chromosomes of the pair considered and the other cell does not contain a chromosome of this pair. A similar result can be obtained during a bad distribution of chromatids during anaphase II.

After fertilization from a gamete of this type, a trisomy or a monosomy is obtained.