Question

The correct sequence of different sub-stages of prophase in meiosis after Leptotene is ____________.
(A) Diplotene
(B) Diakinesis
(C) Zygotene
(D) Pachytene
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (C), (D), (A), (B).
• C. (B), (D), (A), (C).
• D. (C), (B), (D), (A).

Hint:

To easily memorize the correct sequence of Prophase I, use this simple mnemonic:
"Lazy Zebra Plays Double Drums"
- Leptotene \(\rightarrow\) Zygotene \(\rightarrow\) Pachytene \(\rightarrow\) Diplotene \(\rightarrow\) Diakinesis.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Meiosis is a specialized cell division that reduces the chromosome number by half, producing four haploid daughter cells.
Prophase I of meiosis is the longest and most complex phase, divided into five distinct, sequential sub-stages based on chromosomal behavior.

Step 2: Detailed Explanation:
Let us review the five sub-stages of Prophase I in chronological order:
1. Leptotene: Chromosomes begin to condense and become visible under light microscopy as thin threads.
2. Zygotene (C): Homologous chromosomes pair up side-by-side in a process called synapsis, facilitated by the synaptonemal complex, forming bivalents.
3. Pachytene (D): Chromosomes continue to condense, and crossing over (homologous recombination) occurs between non-sister chromatids of homologous chromosomes at recombination nodules.
4. Diplotene (A): The synaptonemal complex dissolves, and homologous chromosomes begin to separate but remain held together at X-shaped structures called chiasmata.
5. Diakinesis (B): Chiasmata terminalization occurs, the nucleolus disappears, and the nuclear envelope breaks down, preparing the cell for metaphase I.
The question asks for the correct sequence of the sub-stages *after* Leptotene:
\[ \text{Zygotene (C)} \rightarrow \text{Pachytene (D)} \rightarrow \text{Diplotene (A)} \rightarrow \text{Diakinesis (B)} \]
This matches the sequence (C), (D), (A), (B).

Step 3: Final Answer:
The correct option is (B).