Question

Match the columns.

	Column I		Column II
P	Zygotene	i	Chromosomes become gradually visible under the light microscope
Q	Diakinesis	ii	Bivalents clearly appear as tetrads
R	Pachytene	iii	Terminalisation of chiasmata
S	Leptotene	iv	Synapsis

• A. (P)-(iv), (Q)-(iii), (R)-(ii), (S)-(i)
• B. (P)-(i), (Q)-(ii), (R)-(iii), (S)-(iv)
• C. (P)-(ii), (Q)-(iii), (R)-(iv), (S)-(i)
• D. (P)-(iv), (Q)-(i), (R)-(iii), (S)-(ii)

Answer 1

Answer: (A)

The Prophase I of Meosis I is further divide into 5 phases - Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis. In the leptotene stage the compaction of chromosomes is continued and they become more visible under light microscope. Second stage is zygotene where chromosomes start pairing together and the process is called synapsis. These paired chromosomes are called homologous chromosomes. In the next phase of pachytene these bilvalent chromosomes now appear as tetrads. Pachytene is also characterized by the appearance of recombination nodules which is the site for non sister chromatids to cross over. During the start of diplotene phase there is dissolution of synaptonemal complex and the homologous chromosomes separate from each other except at the sites where crossover has taken place and form an X shaped structure known as chiasmata. The final phase of diakinesis is where terminalisation of chiasmata takes place.