Question

in most animals, genetic information is transcribed from dna to rna and then translated into protein with high fidelity, preserving the sequence encoded in the genome. however, cephalopods such as octopuses and squids exhibit extensive a-to-i rna editing, a post-transcriptional modification in which adenosine is enzymatically deaminated to inosine, which is read as guanosine during translation. this process results in protein variants not directly encoded by the genome and is particularly prevalent in neural tissue. although energetically costly and evolutionarily rare, this strategy appears to confer behavioral flexibility by allowing tuning of neural proteins, decoupling diversity from genomic information.
7
mark for review
what is the main purpose of the text?
(answer : b)
a it explains a molecular strategy by which certain organisms expand protein diversity through modifications that occur before transcription.
b it introduces an alternative method of promoting protein diversity that does not rely strictly on genomic information.
c it discusses the transcription process of dna to rna in octopuses, which is more complex than that of squids.
d it outlines how rna structure influences the genes directly in cephalopods, resulting in new protein variants in neural tissues.

Explanation:

To determine the main purpose, analyze each option:

• Option A: The text says A - to - I RNA editing is post - transcriptional, not pre - transcriptional. So A is incorrect.
• Option B: The text states that cephalopods use A - to - I RNA editing (a method not strictly relying on genomic information) to create protein variants, thus expanding protein diversity. This matches the main idea.
• Option C: The text does not compare the transcription process of octopuses and squids. So C is incorrect.
• Option D: The text says genetic information is transcribed to RNA then translated, and RNA editing (not RNA structure) leads to new protein variants. So D is incorrect.

Answer:

B. It introduces an alternative method of promoting protein diversity that does not rely strictly on genomic information.