Question

Given below are the two statements
Statement I Only one strand in the transcription unit functions as template and is called antisense strand.
Statement II The coding strand of transcription unit is called sense strand.
In light of the above statements, choose the correct answer from the options given below.

• A. Both statement I and statement II are correct.
• B. Both statement I and statement II are incorrect.
• C. Statement I is correct and statement II is incorrect.
• D. Statement I is incorrect and statement II is correct.

Hint:

Always remember:
Template strand = Antisense strand (\(3' \rightarrow 5'\)).
Coding strand = Sense strand (\(5' \rightarrow 3'\)).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Transcription is the process of copying genetic information from one strand of the DNA into RNA.
A transcription unit in DNA primarily consists of a promoter, the structural gene, and a terminator.

Step 2: Key Formula or Approach:
Analyze the standard nomenclature of DNA strands during transcription based on their polarity (\(5' \rightarrow 3'\) or \(3' \rightarrow 5'\)) and function.

Step 3: Detailed Explanation:
Statement I: Only one strand functions as a template and is called the antisense strand. This is correct because the DNA-dependent RNA polymerase catalyzes polymerization in only the \(5' \rightarrow 3'\) direction, so the strand with \(3' \rightarrow 5'\) polarity acts as the template (antisense strand).
Statement II: The coding strand of the transcription unit is called the sense strand. This is also correct. The other strand with polarity \(5' \rightarrow 3'\) has the exact same sequence as the RNA (except thymine is replaced by uracil) and is appropriately called the coding or sense strand.

Step 4: Final Answer:
Both statements accurately describe the components of a transcription unit, so option (A) is the correct choice.