Question

Assertion (A): In eukaryotes, both introns and exons are transcribed to form hnRNA.

Reason (R): The exons are removed to make the final transcript by splicing.

• A. Both assertion and reason are true and reason is the correct explanation of assertion
• B. Both assertion and reason are true but reason is not the correct explanation of assertion
• C. Assertion is true but the reason is false
• D. Both assertion and reason are false

Answer 1

The correct option is C Assertion is true but the reason is false

The genetic information from one strand of the DNA is copied into RNA during transcription. Hence, synthesis of RNA occurs during transcription.

In eukaryotes, the monocistronic structural genes contain both exons and introns. Exons are the coding sequences (code for amino acids) and introns are the non-coding sequences.

During transcription, both the exons and introns are transcribed to form the pre-mRNA or heterogeneous nuclear RNA (hnRNA). Thus, the assertion holds true.

The hnRNA undergoes post-transcriptional modifications to form the functional mRNA.
The post-transcriptional modifications include a process called splicing in which there is removal of introns and subsequent joining of exons. Therefore, the mature or functional mRNA contains only exons. Hence the reason is false.