Question

Nondisjunction can occur at either the first or the second division of meiosis. XYY individuals would most likely arise from nondisjunction at the ______ meiotic division in the ______?

1) First, egg
2) First, sperm
3) Second, egg
4) Second, sperm

Answer 1

XYY individuals are most likely the result of nondisjunction during the second meiotic division in the sperm, which causes a sperm cell to carry an extra Y chromosome.

Step-by-step explanation:

Nondisjunction can occur during meiosis I or meiosis II, each resulting in different outcomes in terms of gamete formation. XYY individuals would most likely arise from nondisjunction at the second meiotic division in the sperm. During meiosis II, if sister chromatids fail to separate, this results in one gamete with an extra chromosome, in this case, an extra Y chromosome leading to an XYY zygote post-fertilization. This contrasts with meiosis I nondisjunction, which results in two gametes with an additional chromosome and two gametes lacking that chromosome altogether.

Bearing in mind that the sex chromosomes (X and Y) segregate during meiosis, and given that males produce sperm with either an X or a Y chromosome, a failure in separation of the Y chromosome during meiosis II can result in a sperm cell with an extra Y chromosome. If this sperm cell fertilizes an egg, the resulting zygote would have one X chromosome from the egg and two Y chromosomes from the sperm, leading to an XYY male