Q.26 The synaptonemal complex is observed in which phase of prophase-I of meiosis. Leptonema Zygonema Pachynema Diplonema

Q.26 The synaptonemal complex is observed in which phase of prophase-I of meiosis.

  1. Leptonema
  2. Zygonema
  3. Pachynema
  4. Diplonema

    Pachynema (pachytene) is the phase where the fully formed synaptonemal complex is prominently observed during prophase-I of meiosis.

    Option Breakdown

    Leptonema

    Leptonema (leptotene) features chromosome condensation into thin threads with visible chromosome ends (bouquet stage); no synaptonemal complex forms yet.

    Zygonema

    Zygonema (zygotene) initiates homologous chromosome pairing (synapsis) where synaptonemal complex begins assembling at multiple points.

    Pachynema

    Pachynema shows complete synaptonemal complex formation between all homologous chromosome pairs, enabling crossing over; visible under electron microscopy.

    Diplonema

    Diplonema (diplotene) marks synaptonemal complex disassembly as homologs separate except at chiasmata, revealing recombination sites.

    Introduction

    The synaptonemal complex is observed in Pachynema phase of prophase-I meiosis among Leptonema, Zygonema, and Diplonema, crucial for genetic recombination.

    Prophase-I Stages Overview

    Prophase-I divides into five substages where the synaptonemal complex progressively assembles during Zygonema and matures fully in Pachynema for crossover formation.

    Meiosis Stage Comparison

    Stage Synaptonemal Complex Status Key Chromosome Event
    Leptonema Absent Chromosome condensation
    Zygonema Assembly begins Synapsis initiation
    Pachynema Fully formed/visible Crossing over occurs
    Diplonema Begins disassembly Chiasmata formation

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