[Campbell Biology P.313] The data shows a sharp drop in DNA content starting around 7.0 hour... | Practice Question

The data shows a sharp drop in DNA content starting around 7.0 hours. What specific event in meiosis does this 'corner' in the graph, where the downward slope begins, most likely represent?

  • A: The beginning of Prophase I.
  • B: The separation of homologous chromosomes in Anaphase I.
  • C: The separation of sister chromatids in Anaphase II.
  • D: The completion of DNA synthesis (S phase).

Explanation

The peak DNA content approx. 48.0 fg represents the 4C value in G2/Metaphase I. The first major drop in DNA content, where the amount is halved, represents the division of the cell into two haploid cells, each with duplicated chromosomes 2C . This halving is the result of homologous chromosomes separating during Anaphase I and the subsequent cytokinesis.