Question

If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, what will be the chromosome number of the four resulting gametes with respect to the normal haploid number (n)?

a.n + 1; n + 1; n - 1; n - 1
b.n + 1; n - 1; n; n
c.n + 1; n - 1; n - 1; n - 1
d.n + 1; n + 1; n; n
e.n - 1; n - 1; n; n

Answer 1

a.n + 1; n + 1; n - 1; n - 1 During anaphase of meiosis I, if a pair of homologous chromosomes fails to separate, the resulting gametes will have extra and missing chromosomes.

Step-by-step explanation:

Nondisjunction occurs when homologous chromosomes or sister chromatids fail to separate during meiosis, resulting in an abnormal chromosome number. If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, the resulting gametes will have an extra chromosome (n + 1) in two of the gametes and a missing chromosome (n - 1) in the other two gametes. Therefore, the correct option is a. n + 1; n + 1; n - 1; n - 1.

If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, the chromosome number of the four resulting gametes with respect to the normal haploid number (n) would be n + 1, n + 1, n - 1, n - 1. This phenomenon is known as nondisjunction, and it results in an abnormal distribution of chromosomes, where two gametes have an extra chromosome and two gametes are missing a chromosome. An example of a disorder resulting from nondisjunction is trisomy 21, also known as Down Syndrome, which occurs when an individual has an extra copy of chromosome 21.