Question
Which of the following statements is true? a. More gametes will be affected if nondisjunction occurs during anaphase I than if nondisjunction occurs during anaphase II. b. Nondisjunction during anaphase I or anaphase II will have the same effect. c. More gametes will be affected if nondisjunction occurs during anaphase II than if nondisjunction occurs during anaphase I. d. Nondisjunction during anaphase I or anaphase II will have no effect on the gametes formed.
Solution
4.1
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Answer
The correct answer is **a. More gametes will be affected if nondisjunction occurs during anaphase I than if nondisjunction occurs during anaphase II.**Here's why:* **Nondisjunction** is the failure of homologous chromosomes (anaphase I) or sister chromatids (anaphase II) to separate properly during meiosis. This results in some gametes having an extra chromosome and others missing a chromosome.* **Anaphase I:** Homologous chromosomes separate. If nondisjunction occurs here, *all* resulting gametes will be abnormal. Two gametes will have an extra chromosome, and two will be missing a chromosome.* **Anaphase II:** Sister chromatids separate. If nondisjunction occurs here, *half* of the resulting gametes will be abnormal. One gamete will have an extra chromosome, one will be missing a chromosome, and two will be normal.Therefore, nondisjunction in anaphase I affects all four gametes, while nondisjunction in anaphase II affects only two of the four gametes.