Question:
Read the following passage and answer the questions that follow :
The process of copying genetic information from template strand of DNA into RNA is called transcription. It is mediated by RNA polymerase. Transcription takes place in the nucleus of eukaryotic cells. In transcription, only a segment of DNA and only one of the strands is copied into RNA.
(c) Why is only one strand of the DNA transcribed ? Give two reasons.
Read the following passage and answer the questions that follow :
The process of copying genetic information from template strand of DNA into RNA is called transcription. It is mediated by RNA polymerase. Transcription takes place in the nucleus of eukaryotic cells. In transcription, only a segment of DNA and only one of the strands is copied into RNA.
(c) Why is only one strand of the DNA transcribed ? Give two reasons.
Show Hint
Think about the RNAs that two complementary strands would produce.
Updated On: Oct 22, 2026
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Solution and Explanation
Step 1: Think about what would happen if both strands were copied:
The two DNA strands have different base sequences, but they are complementary to each other.
So the RNAs made from the two strands would also be complementary to each other.
Step 2: Reason 1:
The two complementary RNAs would pair and form double-stranded RNA.
Such double-stranded RNA cannot be translated, so the genetic message would be blocked.
Step 3: Reason 2:
The two strands would give two RNAs with different codon sequences, so two different proteins would arise from one segment of DNA.
This would confuse the genetic information. The cell would also waste energy and nucleotides.
Final Answer:
Only one strand is copied because (1) the two RNAs would form a double-stranded RNA and stop translation, and (2) the two strands would code for two different proteins from the same segment, confusing the genetic information.
The two DNA strands have different base sequences, but they are complementary to each other.
So the RNAs made from the two strands would also be complementary to each other.
Step 2: Reason 1:
The two complementary RNAs would pair and form double-stranded RNA.
Such double-stranded RNA cannot be translated, so the genetic message would be blocked.
Step 3: Reason 2:
The two strands would give two RNAs with different codon sequences, so two different proteins would arise from one segment of DNA.
This would confuse the genetic information. The cell would also waste energy and nucleotides.
Final Answer:
Only one strand is copied because (1) the two RNAs would form a double-stranded RNA and stop translation, and (2) the two strands would code for two different proteins from the same segment, confusing the genetic information.
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