Question

Which of the following sites is represented by Loops in lampbrush chromosomes?

• A. Crossing over
• B. Cell division
• C. Replication
• D. Transcription

Answer 1

The Correct Option is D

Lampbrush chromosomes are highly extended meiotic chromosomes found in oocytes of amphibians and some other animals. They exhibit prominent loop structures, which are sites of active transcription. 

Step 1: Understanding Lampbrush Chromosome Loops - These chromosomes have large lateral loops, which represent active gene transcription. - The loops consist of transcriptionally active chromatin, allowing massive RNA synthesis. - This activity is essential for producing large amounts of mRNA needed for oocyte development. 

Step 2: Evaluating the Options - Option (A) - Incorrect: Crossing over occurs during meiosis but is not related to lampbrush loops. 
- Option (B) - Incorrect: Cell division does not directly involve lampbrush chromosome loops. 
- Option (C) - Incorrect: Replication occurs before meiosis but is not the primary function of these loops. 
- Option (D) - Correct: The loops in lampbrush chromosomes represent active transcription. 

Step 3: Conclusion Since lampbrush chromosome loops are sites of active transcription, the correct answer is option (D).