Question

If a pair of homologous chromosomes undergoes nondisjunction during anaphase I of meiosis, what will be the chromosome number of the four resulting gametes? Assume meiosis II is normal.

a) 2n
b) n-1
c) n+1
d) 2n+1

Answer 1

If nondisjunction occurs during anaphase I of meiosis, the four resulting gametes will have abnormal chromosome numbers, with two gametes having n+1 chromosomes and two gametes having n-1 chromosomes.

Step-by-step explanation:

If a pair of homologous chromosomes undergoes nondisjunction during anaphase I of meiosis, and assuming meiosis II proceeds normally, two of the resulting gametes will have an extra chromosome (n+1), and the other two will be missing a chromosome (n-1).

Considering a diploid cell, where 'n' is the number of chromosomes in a normal haploid gamete, nondisjunction during anaphase I means that one pair of homologous chromosomes does not separate properly. The result is that one cell will receive both chromosomes of the pair, and the other cell will receive none.