Pick out the correct statements by given codes below:
A. Synapsis of homologous chromosomes takes place during prophase I of meiosis.
B. Division of centromeres takes place during anaphase - I of meiosis.
C. Spindle fibres disappear completely in the telophase of mitosis.
D. Nucleoli reappear at telophase - I of meiosis.

Question

Pick out the correct statements by given codes below: 
A. Synapsis of homologous chromosomes takes place during prophase I of meiosis. 
B. Division of centromeres takes place during anaphase - I of meiosis. 
C. Spindle fibres disappear completely in the telophase of mitosis. 
D. Nucleoli reappear at telophase - I of meiosis.

Accepted Answer

The correct option is 3: A, C and D

Statement A is correct: **Synapsis of homologous chromosomes takes place during prophase I of meiosis.** This is a defining event of meiosis. Specifically, it occurs during the **zygotene** stage of Prophase I, where the homologous chromosomes align precisely, gene for gene, and are held together by the synaptonemal complex, forming a bivalent or tetrad structure. This pairing is essential for the crossing over and recombination that follows.

Statement C is correct: **Spindle fibres disappear completely in the telophase of mitosis.** As a cell concludes either mitosis or meiosis, the microtubules that formed the spindle apparatus—which was responsible for separating the chromosomes—are completely disassembled (depolymerized) during telophase. This allows the nuclear envelope to reform around the two new sets of chromosomes, finalizing the division process.

Statement D is correct: **Nucleoli reappear at telophase - I of meiosis.** The nucleolus, which is the site of ribosomal RNA synthesis and ribosome assembly, disorganizes and disappears during the prophase stage of both mitosis and meiosis. Its reformation, or reappearance, occurs late in telophase I (and telophase II/telophase of mitosis) as the chromosomes decondense and the nuclear organizing regions (NORs) are reactivated in the newly forming daughter nuclei. Since A, C, and D are all correct descriptions of events in cell division, Option 3 is the correct choice.

The incorrect option is 1: A only

While statement A is factually correct, choosing "A only" implies that statements C and D are incorrect, which is not true. Both the disassembly of the spindle fibers (C) and the reappearance of the nucleoli (D) are characteristic and correct events associated with the telophase stage of the respective division cycles (mitosis and meiosis I). Therefore, this option is incomplete and fails to acknowledge all the correct statements.

The incorrect option is 2: A and B

Statement B is incorrect because **Division of centromeres takes place during anaphase - II of meiosis, not anaphase - I.** Meiosis I is a **reductional division**, where homologous chromosomes separate, but the centromeres holding the sister chromatids together remain intact. The actual division of the centromere, which allows sister chromatids to finally separate, is a key event that occurs later during **Anaphase II** (or Anaphase of mitosis), but not in Anaphase I. Pairing statement A (correct) with B (incorrect) makes this option incorrect overall.

The incorrect option is 4: A and C

This option is incorrect because it is incomplete. While statements A (synapsis in Prophase I) and C (spindle disappearance in Mitosis Telophase) are individually correct, the option ignores statement D, which is also correct. The reappearance of the nucleoli in Telophase I is a standard and expected event as the cell prepares for Meiosis II, re-establishing nuclear organization. Since an accurate code must include all correct statements, choosing only A and C is an insufficient selection.