What is the advantage of the 5' cap and the poly A tail?

• A. They destabilize mRNA
• B. They protect RNA from degradation and help in export and translation
• C. They inhibit ribosome binding
• D. They are only found in prokaryotes

Answer: (B)

The main idea is that the 5' cap and the poly(A) tail are protective and functional features of eukaryotic mRNA that boost stability, export from the nucleus, and efficient translation.

The 5' cap is a modified guanine added early in transcription. It protects the 5' end from degradation by 5' exonucleases and acts as a recognition signal for cap-binding proteins that recruit translation initiation factors, helping the ribosome recognize and start translating the mRNA.

The poly(A) tail at the 3' end increases mRNA stability by blocking 3' to 5' exonucleases. It also aids nuclear export through interactions with export factors and enhances translation by binding poly(A)-binding proteins that interact with translation factors, promoting a circular mRNA structure that improves ribosome recycling and overall translation efficiency.

So the advantage is improved RNA stability plus better export and translation. These features do not destabilize RNA, do not inhibit ribosome binding, and are characteristic of eukaryotes rather than prokaryotes.