What is the function of the 5' cap and 3' poly-A tail in eukaryotic mRNA?

What is the function of the 5' cap and 3' poly-A tail in eukaryotic mRNA?

• A. They protect mRNA from degradation, aid export from the nucleus, and enhance translation.
• B. They encode start and stop signals for translation.
• C. They are only present in prokaryotic mRNA.
• D. They determine the amino acid sequence of the protein.

Answer: (A)

In eukaryotes, mRNA maturation adds a 5' cap and a 3' poly-A tail to protect the message and regulate its use. The 5' cap is a modified guanine that helps shield the transcript from degradation right at the start and serves as a landing pad for proteins that guide the ribosome to the mRNA, kick-starting translation. The 3' poly-A tail, a long stretch of adenines, protects the end from exonucleases, supports efficient export of the mRNA from the nucleus to the cytoplasm, and, with binding proteins, enhances translation by helping the ribosome recycle and reinitiate more effectively. Together, these features increase mRNA stability, ensure it reaches the cytoplasm, and boost how well it's translated into protein. These roles aren’t about encoding start and stop signals or determining the amino acid sequence; those functions come from the genetic code and the sequence of codons in the mRNA. Also, these modifications are characteristic of eukaryotic mRNA, not typical for prokaryotic mRNA.

In eukaryotes, mRNA maturation adds a 5' cap and a 3' poly-A tail to protect the message and regulate its use. The 5' cap is a modified guanine that helps shield the transcript from degradation right at the start and serves as a landing pad for proteins that guide the ribosome to the mRNA, kick-starting translation. The 3' poly-A tail, a long stretch of adenines, protects the end from exonucleases, supports efficient export of the mRNA from the nucleus to the cytoplasm, and, with binding proteins, enhances translation by helping the ribosome recycle and reinitiate more effectively. Together, these features increase mRNA stability, ensure it reaches the cytoplasm, and boost how well it's translated into protein.

These roles aren’t about encoding start and stop signals or determining the amino acid sequence; those functions come from the genetic code and the sequence of codons in the mRNA. Also, these modifications are characteristic of eukaryotic mRNA, not typical for prokaryotic mRNA.