Question

Arrange the following stages in Prophase-I in the order of occurrence.
A. Zygotene
B. Leptotene
C. Diplotene
D. Pachytene
Choose the correct answer from the options given below:

• A. A, B, C, D
• B. D, B, C, A
• C. B, A, D, C
• D. C, B, D, A

Hint:

A useful mnemonic for the stages of Prophase I is: "{L}azy {Z}ebras {P}ush {D}own {D}aisies" for {L}eptotene, {Z}ygotene, {P}achytene, {D}iplotene, {D}iakinesis.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Prophase I of meiosis is a complex phase where homologous chromosomes pair and exchange genetic material. It is divided into five distinct sub-stages. The question asks for the correct sequence of four of these stages.
Step 2: Detailed Explanation:
The five stages of Prophase I occur in the following order:
1. Leptotene: Chromosomes begin to condense and become visible.
2. Zygotene: Homologous chromosomes pair up (synapsis) to form bivalents.
3. Pachytene: Crossing over occurs, where genetic material is exchanged between non-sister chromatids.
4. Diplotene: Homologous chromosomes begin to separate but remain attached at points called chiasmata (sites of crossing over).
5. Diakinesis: Chromosomes fully condense, and the nuclear envelope breaks down.
Step 3: Final Answer:
Matching the given stages to the correct order:
- B. Leptotene (1st)
- A. Zygotene (2nd)
- D. Pachytene (3rd)
- C. Diplotene (4th)
The correct sequence is B, A, D, C.