If nondisjunction occurs during meiosis II, as shown in the image below, what types gametes are produced from the original diploid cell? Click on all the boxes that apply.
The Correct Answer and Explanation is:
The correct answers are:
- Abnormal (n+1)
- Abnormal (n+1)
- Abnormal (n–1)
- Normal (n)
Explanation:
Nondisjunction is the failure of sister chromatids to separate properly during meiosis II. In the image, nondisjunction occurs in one of the two cells produced from meiosis I. This results in both sister chromatids moving to the same daughter cell, rather than being evenly distributed. Consequently, the gametes formed from this abnormal division will have an incorrect number of chromosomes.
From this event, four gametes are ultimately produced:
- One gamete receives both sister chromatids. This gamete ends up with an extra chromosome, labeled as Abnormal (n+1).
- One gamete receives no chromosome from the affected pair. It becomes Abnormal (n–1).
- The other two gametes arise from the unaffected cell of meiosis I, which proceeds through meiosis II normally. Each of these produces a gamete with the correct haploid number, Normal (n).
However, in the image provided, only three abnormal gametes are displayed as options: two with (n+1) and one with (n–1). The correct set of possible gametes includes all of these plus one normal (n) gamete.
Therefore, the correct boxes to check are:
- Abnormal (n+1) (two gametes)
- Abnormal (n–1) (one gamete)
- Normal (n) (not shown in the image, but logically included based on meiosis mechanics)
This illustrates how nondisjunction in meiosis II produces a combination of abnormal and normal gametes due to errors in the separation of sister chromatids in only one cell, while the other cell undergoes normal division.
