Q.50 Identify the event that exclusively occurs in meiotic cell division
(A) Chromatid formation (B) Spindle formation
(C) Synapsis (D) Chromosome movement to pole
Meiosis Exclusive Event: Synapsis vs Mitosis Processes
Meiotic division produces gametes with half chromosome number and genetic diversity through unique pairing. While mitosis and meiosis share basic machinery, one event defines meiosis. Synapsis during prophase I enables homologous recombination.
Correct Answer
(C) Synapsis. This homologous chromosome pairing with synaptonemal complex formation occurs only in meiosis I prophase, absent in mitosis.
Meiosis vs Mitosis Events
Mitosis duplicates cells identically; meiosis halves chromosomes via two divisions post-one replication. Shared: spindle assembly, chromatid formation (S-phase), anaphase movement. Meiosis-unique: synapsis, crossing over, homolog separation.
Process Details
Synapsis aligns maternal/paternal homologs via zipper-like synaptonemal complex. Enables chiasmata for genetic shuffling. Lacks in mitosis where sister chromatids (not homologs) align independently.
Option Analysis
| Option | Event | Meiosis Exclusive? | Reason |
|---|---|---|---|
| (A) | Chromatid formation | No | Occurs in S-phase before both mitosis and meiosis I. |
| (B) | Spindle formation | No | Mitotic/meiotic spindle assembles in both for chromosome segregation. |
| (C) | Synapsis | Yes | Homologous pairing only in prophase I; critical for recombination . |
| (D) | Chromosome movement to pole | No | Anaphase I/II and mitosis anaphase pull chromosomes via microtubules. |
Exam Tips
Mnemonic: Synapsis = Special to meiosis. Prophase I sub-stages (leptotene-zygotene-pachytene) feature synapsis. Mitosis skips homolog pairing entirely.
