Question

Assertion :The expression of cellular genetic information is unidirectional. Reason: Cancer virus goes topsy turvy, therefore reverse transcription allows a sequence of RNA to be retrieved and used as genetic information.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

According to Crick, gene expression follows a unidirectional path from DNA to RNA to protein. DNA sequence is transcribed into RNA which in turn is translated into a polypeptide sequence. The information does not flow backwards and hence, once translated, the RNA sequence can not be retrieved. But the cancer viruses, which are RNA retroviruses, synthesize DNA using their RNA as a template via reverse transcription; a process carried out by reverse transcriptase enzyme. The synthesized DNA, cDNA, is inserted into a host and transcribed into RNA which in turn is translated into polypeptides. Here, RNA sequence is retrieved and is used to produce DNA. But reverse transcription makes the flow of genetic information bi-directional. Thus, the correct answer is option B.