Question

Identify the correct combination regarding anaphase, anaphase-I and anaphase-II.

• A. Anaphase: Centromere splits
  Anaphase- I: Centromere splits
  Anaphase- II: Centromere splits
• B. Anaphase: Chromatids move to opposite poles
  Anaphase- I: Homologous chromosomes separate
  Anaphase- II: Centromere splits
• C. Anaphase: Chromosomes cluster at opposite poles
  Anaphase- I: Homologous chromosomes separate
  Anaphase- II: Centromere splits
• D. Anaphase: Chromosomes move to opposite poles
  Anaphase- I: Homologous chromosomes separate
  Anaphase- II: Centromere splits

Answer 1

Answer: (B)

Anaphase: Chromatids move to opposite poles

Anaphase- I: Homologous chromosomes separate
Anaphase- II: Centromere splits
Anaphase I of meiosis I is characterised by shortening of kinetochore microtubules shorten which in turn pulls the homologous chromosomes apart and drives them to move towards the opposite poles. This makes option C incorrect as anaphase chromosomes just start moving towards the opposite poles.
At this stage, each chromosomes contains a pair of sister chromatids. At the end of anaphase I, two haploids sets are present at two ends of the cell. Option A is incorrect as centromeres do not split during anaphase I.
Anaphase II is characterized by splitting of centromere to pull the sister chromatid apart which then move towards the opposite poles. Option D is incorrect as chromatid is the newly synthesized copy (during S phase) of parental chromosome which remain attached to the parental chromosome via centromere. Hence, we call them sister or non sister chromatids (of the same or different chromosomes respectively) till they are separated from each other by splitting of centromere during anaphase II of meiosis and anaphase of mitosis. This makes option B correct answer.