Crossing Over: Stage of Meiosis
View Complete Answer & Explanation
Question (English)
Crossing over (recombination) takes place during which stage of meiosis?
- Pachytene stage of Prophase-I ✓ Correct
- Diplotene stage of Prophase-I
- Metaphase of Meiosis I
- Metaphase of Meiosis II
Explanation:
Correct Answer: Pachytene Stage of Prophase-I
From the notes: Crossing over = exchange of segment between non-sister chromatids of homologous chromosomes in the pachytene stage of Meiosis-I (Prophase-I).
Stages of Prophase-I (Mnemonic: LZPDD)
- Leptotene: Chromosomes begin to condense
- Zygotene: Homologous chromosomes begin to pair (synapsis); synaptonemal complex forms
- Pachytene: Full synapsis complete; crossing over occurs ✔; chiasmata form
- Diplotene: Bivalents begin to repel; chiasmata become visible
- Diakinesis: Chromosomes maximally condensed; nuclear envelope breaks down
Significance
Crossing over is the 2nd biggest cause of genetic variation (after segregation). It creates new combinations of alleles on chromosomes, which is important for evolution and for breaking up unfavourable linkages in breeding programmes.
📚 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.
