| Column-I | Column–II | ||
| a. | Pachytene | (i) | The pairing of homologous chromosomes |
| b. | Metaphase I | (ii) | Terminalization of chiasmata |
| c. | Diakinesis | (iii) | Crossing-over takes place |
| d. | Zygotene | (iv) | Chromosomes align at the equatorial plate |
Match the stages of meiosis of Column-I to their characteristic features in Column-II and select the correct…
- $\begin{array}{|l|l|l|l|} \hline a & b & c & d \\ \hline \text{(iii)} & \text{(iv)} & \text{(ii)} & \text{(i)} \\ \hline \end{array}$
- $\begin{array}{|l|l|l|l|} \hline a & b & c & d \\ \hline \text{(i)} & \text{(iv)} & \text{(ii)} & \text{(iii)} \\ \hline \end{array}$
- $\begin{array}{|l|l|l|l|} \hline a & b & c & d \\ \hline \text{(ii)} & \text{(iv)} & \text{(iii)} & \text{(i)} \\ \hline \end{array}$
- $\begin{array}{|l|l|l|l|} \hline a & b & c & d \\ \hline \text{(iv)} & \text{(iii)} & \text{(ii)} & \text{(i)} \\ \hline \end{array}$
Solution
Zygotene:
- Chromosomes start pairing together. This process is called synapsis. The paired chromosomes are called homologous chromosomes.
- The formation of synapsis is accompanied by the formation of the synaptonemal complex.
- The synaptonemal complex by a pair of homologous chromosomes is called a bivalent or a tetrad.
Pachytene:
- Bivalent chromosomes clearly appear as tetrads, at this stage.
- Recombination nodules appear. These nodules are the sites at which crossing overtakes place between non-sister chromatids of the homologous chromosomes.
- The exchange of genetic materials between two homologous chromosomes takes place during crossing over. This leads to the recombination of genetic materials on the two chromosomes.
Diakinesis:
- Chiasmata is terminated at this stage.
- Meiotic spindles are formed to prepare the homologous chromosomes for separation.
- The nucleolus disappears and the nuclear envelope breaks down by the end of diakinesis.
Metaphase I:
- The bivalent chromosomes are aligned on the equatorial plate.
- Spindle fibres from opposite poles attach to the pair of homologous chromosomes.
Asked in: NEET 2016 (Phase 2)
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