Question

Match the column I with column II and select the correct answer.

• 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

Answer: (B)

A-iv, B-v, C-ii, D-i, E-iii

1. The pachytene - At this point a tetrad of the chromosomes has formed known as a bivalent. This is the stage when chromosomal crossover (crossing over) occurs. Non-sister chromatids of homologous chromosomes may exchange segments over regions of homology.

2. The zygotene stage - occurs as the chromosomes approximately line up with each other into homologous chromosome pairs. In some organisms, this is called as the bouquet stage because of the way the telomeres cluster at one end of the nucleus. At this stage, the synapsis of homologous chromosomes takes place, facilitated by assembly of central element of the synaptonemal complex.

3. During the diplotene stage, the synaptonemal complex degrades and homologous chromosomes separate from one another a little. The chromosomes themselves uncoil a bit, allowing some transcription of DNA. However, the homologous chromosomes of each bivalent remain tightly bound at chiasmata, the regions where crossing-over occurred.

4. 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.

5. During leptotene, lateral elements of the synaptonemal complex assemble.

6. Chromosomes condense further during the diakinesis stage. This is the first point in meiosis where the four parts of the tetrads are actually visible. Sites of crossing over entangle together, effectively overlapping, making chiasmata clearly visible. During this stage terminalization occurs.
Thus, option B is correct.