Stage of Crossing Over in Meiosis
Crossing over takes place in:
- Pachytene stage of prophase-I — Correct Answer
- Diplotene stage of prophase-I
- Metaphase of meiosis I
- Metaphase of meiosis II
Explanation:
Correct Answer: Pachytene stage of Prophase-I
Crossing over is the exchange of segments between non-sister chromatids of homologous chromosomes. It occurs specifically during the Pachytene substage of Prophase I of Meiosis-I.
Stages of Prophase-I
| Substage | Key Event |
|---|---|
| Leptotene | Chromosomes begin to condense and become visible |
| Zygotene | Homologous chromosomes begin to pair (synapsis) — Bivalent formation |
| Pachytene | Crossing over occurs (exchange between non-sister chromatids of homologs) |
| Diplotene | Chiasmata visible; homologs begin to separate |
| Diakinesis | Complete condensation; spindle formation begins |
Importance of Crossing Over
- Crossing over is the 2nd largest cause of genetic variation (after segregation).
- It creates new combinations of alleles — recombinant gametes.
- Translocation (different from crossing over): Exchange between non-homologous chromosomes.
📚 About this Topic — Animal Genetics & Breeding
This multiple choice question is from Animal Genetics & Breeding, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Genetics & Breeding to strengthen your preparation.
