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Multiple Choice
Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct?
A
The 5' end is the site of polyadenylation.
B
The 5' end is always capped with a methyl group.
C
The 5' end is where the ribosome binds during translation.
D
The 5' end typically has a phosphate group attached.
Verified step by step guidance
1
Understand the structure of an RNA molecule: RNA is a single-stranded nucleic acid composed of nucleotides, each consisting of a sugar, a phosphate group, and a nitrogenous base.
Identify the orientation of the RNA strand: RNA strands have directionality, with a 5' (five prime) end and a 3' (three prime) end. This directionality is crucial for various biological processes.
Examine the characteristics of the 5' end: The 5' end of an RNA strand is characterized by the presence of a phosphate group attached to the 5' carbon of the ribose sugar. This is a key feature that distinguishes the 5' end from the 3' end.
Consider the process of capping: In eukaryotic cells, the 5' end of an RNA molecule is often modified by the addition of a 7-methylguanylate cap. However, this cap is not a methyl group directly attached to the 5' end but rather a complex structure added after transcription.
Clarify the role of the 5' end in translation: While the 5' end is important for translation initiation, it is not the site where the ribosome directly binds. Instead, the ribosome binds to the mRNA at the start codon, which is typically downstream of the 5' cap structure.