Q.30 Which one of the following is the correct sequence of prophase-I stage?
- Leptotene, Pachytene, Zygotene, Diplotene, Diakinesis
- Leptotene, Zygotene, Pachytene, Diakinesis, Diplotene
- Zygotene, Leptotene, Pachytene, Diplotene, Diakinesis
- Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis
The correct sequence of prophase-I stages is Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.
Introduction
Prophase I stages sequence leptotene zygotene pachytene defines meiosis I’s longest phase, enabling homologous recombination for genetic diversity. This guide breaks down the exact order, evaluates all MCQ options, and highlights key chromosomal events for biology exam success.
Correct Sequence
Prophase I divides into five substages progressing as:
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Leptotene: Chromosomes condense into thin threads; axial elements form.​
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Zygotene: Homologous chromosomes pair (synapsis) via synaptonemal complex.​
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Pachytene: Crossing over occurs between non-sister chromatids.​
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Diplotene: Synaptonemal complex dissolves; chiasmata visible, holding homologs.​
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Diakinesis: Chromosomes fully condense; nuclear envelope breaks down.​
This sequence supports genetic variation through recombination.​
Option Analysis
Option Sequence Correct? Reason 1 Leptotene, Pachytene, Zygotene, Diplotene, Diakinesis No ​ Pachytene follows Zygotene, not precedes it; skips proper pairing order. 2 Leptotene, Zygotene, Pachytene, Diakinesis, Diplotene No ​ Diakinesis precedes Diplotene; final condensation happens last. 3 Zygotene, Leptotene, Pachytene, Diplotene, Diakinesis No ​ Leptotene initiates condensation before Zygotene pairing. 4 Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis Yes ​ Matches standard progression: condensation → pairing → crossing over → separation → metaphase prep. Meiosis Context
Prophase I lasts longest (days in some species), ensuring synapsis and chiasmata formation for proper segregation in metaphase I. Errors here cause aneuploidy; vital for NEET-level genetics.
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