Question

Match the column–I with column–II and select the correct answer:

Column-I	Column-II
(a) Pachytene	(i) Condensation
(b) Zygotene	(ii) Chiasma visible
(c) Diplotene	(iii) Terminalisation
(d) Leptotene	(iv) Gene exchange
(e) Diakinesis	(v) Synapsis

• A. a–i, b–ii, c–iii, d–iv, e–v
• B. a–iv, b–v, c–ii, d–i, e–iii
• C. a–iii, b–iv, c–v, d–ii, e–i
• D. a–ii, b–iii, c–iv, d–i, e–v

Answer 1

The correct option is B a–iv, b–v, c–ii, d–i, e–iii

The prophase I of meiosis I is divided into five phases - leptotene, zygotene, pachytene, diplotene and diakinesis.

Leptotene: The first stage of prophase I is the leptotene stage. In this stage of prophase I, individual chromosomes each consisting of two sister chromatids condense from the diffuse interphase conformation into visible strands within the nucleus. However, the two sister chromatids are still so tightly bound that they are indistinguishable from one another.

Zygotene: It occurs as the chromosomes approximately line up with each other into homologous chromosome pairs. At this stage, the synapsis of homologous chromosomes takes place, facilitated by assembly of central element of the synaptonemal complex.

Pachytene: This is the stage when chromosomal crossover (crossing over) occurs where there is exchanged of genetic material. Non-sister chromatids of homologous chromosomes may exchange segments over regions of homology.

Diplotene: The synaptonemal complex degrades and homologous chromosomes separate from one another a little. The homologous chromosomes of each bivalent remain tightly bound at chiasmata, the regions where crossing-over occurred. Chiasmata are clearly visible at this stage.

Diakinesis: The final stage of meiotic prophase I is diakinesis. This is marked by terminalisation of chiasmata. During this phase, the meiotic spindle is assembled to prepare the homologous chromosomes for separation.