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 Problem:
A transcription unit in DNA contains two antiparallel strands, but only one is transcribed into RNA by RNA polymerase.
The enzyme reads the DNA template in the \(3' \rightarrow 5'\) direction to synthesize RNA in the \(5' \rightarrow 3'\) direction.
Step 2: Approach and Formula:
Correlate the polarity and function of each DNA strand with its specific scientific names (template vs. coding, and antisense vs. sense).
Step 3: Detailed Explanation:
Regarding Statement I: The DNA strand with \(3' \rightarrow 5'\) polarity physically acts as the template for RNA synthesis.
Because its sequence is complementary to the final RNA sequence, it is correctly known as the template strand, non-coding strand, or antisense strand.
Hence, Statement I is correct.
Regarding Statement II: The opposite strand with \(5' \rightarrow 3'\) polarity has the exact same sequence as the newly synthesized mRNA (replacing Thymine with Uracil).
Even though it does not serve as the template, it is appropriately called the coding strand or the sense strand.
Hence, Statement II is also correct.
Step 4: Final Answer:
Both statement I and statement II are correct.