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Q.
Correctly identify the stage of cell division shown in the given diagram.
NTA AbhyasNTA Abhyas 2020Cell Cycle and Cell Division
Solution:
Prophase - I
- It is subdivided into 5 phases :
$A.$ Leptotene (Lepto = thin or delicate)
- Chromosomes gradually become visible.
- Condensation or compaction of the chromosomes continues.
$B.$ Zygotene (Zygo = related to pairing or joining)
- Synapsis or pairing of chromosomes occur to bring the homologous chromosomes together.
- Synapsis is followed by the formation of synaptonemal complex (or bivalent or tetrad).
$C.$ Pachytene (Pachy = thick)
- Bivalent chromosomes clearly appear as tetrad as condensation is in progress.
- In this stage crossing over occurs.
$D.$ Diplotene (Diplo = double)
- Starting of diplotene is characterized by the dissolution of the synaptonemal complex and the
separation of the homologous chromosomes from each other except at the X shaped sites of cross
over. These X shapes sites are termed as Chiasmata.
$E.$ Diakinesis (= Movement or separation of both)
- It is characterized by the terminalization of chiasmata.
