Question

What is needed in determining to assess whether a nondisjunction event occurred at meiosis I or meiosis II?

A The karyotype
B Whether the abnormal gamete contributed two copies of the same chromosome or one of each homolog
C The parent of origin of the nondisjunction
D Whether or not recombination occurred between the homologs of the nondisjoined chromosome
E Cannot be determined

Answer 1

To determine if a nondisjunction event occurred at meiosis I or II, it is necessary to examine if the abnormal gamete contributed two copies of the same chromosome or one of each homolog, which can be revealed through the karyotype.

Step-by-step explanation:

To assess whether a nondisjunction event occurred at meiosis I or meiosis II, we need to examine the outcome of the gametes produced. In meiosis I nondisjunction, homologous chromosomes fail to separate, creating two gametes that lack that chromosome and two gametes with two copies. In meiosis II nondisjunction, the sister chromatids fail to separate, which leads to one gamete without the chromosome, two normal gametes with one chromosome copy, and one gamete with two chromosome copies. Therefore, the correct answer is B: Whether the abnormal gamete contributed two copies of the same chromosome or one of each homolog. The karyotype of the offspring that results from these gametes can reveal the pattern of chromosome distribution and help confirm the occurrence and timing of the nondisjunction event.