5' cap protecting mRNA is which molecule?

5' cap protecting mRNA is which molecule?

• A. Guanosine triphosphate
• B. Methyl adenine
• C. Methyl Guanosine
• D. Guanosine

Answer: (C)

The 5' cap on eukaryotic mRNA is a modified guanine nucleotide. Specifically, a methylated guanosine, usually 7-methylguanosine, is attached to the 5' end of the mRNA via a 5'-5' triphosphate bridge to the first nucleotide. This cap protects the mRNA from 5' exonucleases and helps recruit the translation machinery. Why this is the best match: the key feature of the cap is that it is a guanine base that has been methylated, forming a methyl guanosine cap (often referred to as m7G). The other options don’t capture this combination of guanine plus methylation in the cap structure: GTP is just a nucleotide triphosphate used in energy and synthesis; methyl adenine is a methylated adenine, not the cap guanine; guanosine is the unmethylated guanosine nucleoside without the necessary 5'-5' linkage and methylation.

The 5' cap on eukaryotic mRNA is a modified guanine nucleotide. Specifically, a methylated guanosine, usually 7-methylguanosine, is attached to the 5' end of the mRNA via a 5'-5' triphosphate bridge to the first nucleotide. This cap protects the mRNA from 5' exonucleases and helps recruit the translation machinery.

Why this is the best match: the key feature of the cap is that it is a guanine base that has been methylated, forming a methyl guanosine cap (often referred to as m7G). The other options don’t capture this combination of guanine plus methylation in the cap structure: GTP is just a nucleotide triphosphate used in energy and synthesis; methyl adenine is a methylated adenine, not the cap guanine; guanosine is the unmethylated guanosine nucleoside without the necessary 5'-5' linkage and methylation.