Question

Answer the following questions:
(A) Stability of DNA is higher than that of RNA. How?
(B) What are the roles of the three parts of the transcription unit?

Hint:

Understanding the stability of DNA and RNA, and the transcription process, is crucial for molecular biology, particularly in gene expression and regulation.

Answer 1

Step 1: Stability of DNA compared to RNA.
DNA is more stable than RNA due to the following reasons:
1. Double-stranded structure: DNA exists as a double-stranded helix, which provides greater stability. The double-strand structure helps in protecting the genetic information against damage.
2. Deoxyribose sugar: DNA contains deoxyribose, which lacks a hydroxyl group at the 2' position (compared to RNA, which contains ribose with a hydroxyl group at the 2' position). The absence of this hydroxyl group makes DNA less reactive and more stable.
3. Longer lifespan: DNA is designed to store genetic information for long periods, whereas RNA is more transient and involved in protein synthesis.
Step 2: The roles of the three parts of the transcription unit.
The transcription unit consists of three main parts:
1. Promoter: The promoter is a region of DNA that initiates transcription. It is recognized by RNA polymerase, which binds to it and begins the transcription process.
2. Coding Region: The coding region is the part of the DNA that contains the gene to be transcribed into RNA. This is the portion that is ultimately used to synthesize proteins.
3. Terminator: The terminator is a sequence that signals the end of transcription. When RNA polymerase reaches this sequence, it stops synthesizing RNA and releases the RNA transcript.
Step 3: Conclusion.
DNA is more stable than RNA due to its structural properties, while the three parts of the transcription unit (promoter, coding region, and terminator) play crucial roles in the process of gene transcription.