The 7-methylguanosine cap of eukaryotic mRNAs serves which of the following functions?

• A. Promotes splicing of introns from pre-mRNA
• B. Facilitates ribosome binding during translation initiation
• C. Serves as a template for DNA synthesis
• D. Acts as a signal for polyadenylation at the 3' end

Answer: (B)

Verified step by step guidance

1. Understand the structure and function of the 7-methylguanosine cap: The 7-methylguanosine cap is a modified guanine nucleotide added to the 5' end of eukaryotic mRNA during transcription. It plays a critical role in mRNA stability and translation.
2. Review the process of translation initiation: Translation initiation involves the assembly of the ribosome on the mRNA. The 7-methylguanosine cap helps recruit initiation factors and the ribosome to the mRNA, facilitating the start of protein synthesis.
3. Eliminate incorrect options: Analyze each option provided in the question. For example, the cap does not directly promote splicing of introns, serve as a template for DNA synthesis, or act as a signal for polyadenylation at the 3' end.
4. Focus on the correct function: The cap facilitates ribosome binding during translation initiation by interacting with specific proteins, such as the cap-binding complex, which helps position the ribosome correctly on the mRNA.
5. Conclude the reasoning: Based on the biological role of the 7-methylguanosine cap, the correct answer is that it facilitates ribosome binding during translation initiation, ensuring efficient protein synthesis.