Which statement about the 5' cap is true?

Which statement about the 5' cap is true?

• A. Signals polyadenylation
• B. Guides splicing
• C. Initiates transcription
• D. Promotes stability, aids in export, and enhances translation initiation

Answer: (D)

The 5' cap serves as a protective and functional handle for the mRNA. It is added soon after transcription starts and is recognized by cap-binding proteins that recruit the machinery for mRNA processing and use. This cap protects the transcript from 5' exonucleases, helps with export from the nucleus to the cytoplasm, and is crucial for translation initiation by enabling recruitment of initiation factors that bring in the ribosome. It’s not responsible for signaling polyadenylation at the 3' end, it doesn’t directly guide splicing, and it doesn’t initiate transcription. Because it combines stability, export, and translation initiation roles, the statement that the 5' cap promotes stability, aids in export, and enhances translation initiation is the best description.

The 5' cap serves as a protective and functional handle for the mRNA. It is added soon after transcription starts and is recognized by cap-binding proteins that recruit the machinery for mRNA processing and use. This cap protects the transcript from 5' exonucleases, helps with export from the nucleus to the cytoplasm, and is crucial for translation initiation by enabling recruitment of initiation factors that bring in the ribosome. It’s not responsible for signaling polyadenylation at the 3' end, it doesn’t directly guide splicing, and it doesn’t initiate transcription. Because it combines stability, export, and translation initiation roles, the statement that the 5' cap promotes stability, aids in export, and enhances translation initiation is the best description.