- Exam
- NEET
- Year
- 2020
- Subject
- Botany
- Chapter
- Cell Cycle and Cell Division
NEET 2020 · Botany · Cell Cycle and Cell Division
Match the following with respect to meiosis (a) Zygotene (i)...
Match the following with respect to meiosis
| (a) | Zygotene | (i) | Terminalization |
| (b) | Pachytene | (ii) | Chiasmata |
| (c) | Diplotene | (iii) | Crossing over |
| (d) | Diakinesis | (iv) | Synapsis |
Select the correct option from the following
Options
- A(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
- B(a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)
- C(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
- D(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
Correct answer
A. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
Step-by-step solution
Prophase I:
Prophase in meiosis-I is typically longer and more complex than the prophase in meiosis II. Prophase I is subdivided into five phases, viz. Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis.
Leptotene:
• During this stage, the chromosomes become gradually visible under the light microscope. The compaction of chromosomes continues throughout this phase.
Zygotene:
• Chromosomes start pairing together. This process is called synapsis. The paired chromosomes are called homologous chromosomes.
• 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.
• 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.
Diplotene:
• Synapotnemal complex is dissolved at this stage.
• The recombined homologous chromosomes of the bivalent separate from each other; except at the site of crossing over.
• The X-shaped structures; thus formed; are called chiasmata.
Diakinesis:
• Chiasmata is terminated at this stage.
• Meiotic spindles are formed to prepare the homologous chromosomes for separation.
• Nucleolus disappears and nuclear envelope breaks down by the end of diakinesis.