The 5' end modified with the addition of a(n) _________ and the 3' end is modified with the addition of a(n) ___________ tail, both of which stabilize the mRNA molecule.

The 5' end modified with the addition of a(n) _________ and the 3' end is modified with the addition of a(n) ___________ tail, both of which stabilize the mRNA molecule.

• A. poly-A; cap
• B. cap; poly-G
• C. cap; poly-A
• D. poly-C; cap

Answer: (C)

In eukaryotic mRNA, processing adds two key features that protect the message and help it be read by the machinery: a cap at the 5' end and a poly-A tail at the 3' end. The 5' cap is a modified guanine nucleotide that sits on the first nucleotide of the transcript. It guards the mRNA from 5' exonucleases and is recognized by cap-binding proteins, which also help initiate translation. The 3' end gets a poly-A tail, a long stretch of adenine nucleotides added after transcription. This tail protects against 3' exonucleases, aids in exporting the mRNA from the nucleus, and enhances translation efficiency by promoting ribosome recruitment. Therefore, the correct combination is a cap at the 5' end and a poly-A tail at the 3' end. The options proposing other tails (like poly-G or poly-C) or swapped locations don’t match how eukaryotic mRNA is processed.

In eukaryotic mRNA, processing adds two key features that protect the message and help it be read by the machinery: a cap at the 5' end and a poly-A tail at the 3' end. The 5' cap is a modified guanine nucleotide that sits on the first nucleotide of the transcript. It guards the mRNA from 5' exonucleases and is recognized by cap-binding proteins, which also help initiate translation. The 3' end gets a poly-A tail, a long stretch of adenine nucleotides added after transcription. This tail protects against 3' exonucleases, aids in exporting the mRNA from the nucleus, and enhances translation efficiency by promoting ribosome recruitment.

Therefore, the correct combination is a cap at the 5' end and a poly-A tail at the 3' end. The options proposing other tails (like poly-G or poly-C) or swapped locations don’t match how eukaryotic mRNA is processed.