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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