Which of the following is a correct statement about mRNA?
A) mRNA includes a cap that consists of extra adenine nucleotides.
B) mRNA moves from the nucleus to the cytoplasm following RNA processing.
C) mRNA is transcribed from DNA in the cytoplasm.
D) mRNA binds directly to amino acids during translation.
The Correct Answer and Explanation is:
The correct answer is b) mRNA moves from the nucleus to the cytoplasm following RNA processing.
Explanation:
mRNA (messenger RNA) is a crucial molecule in the process of gene expression, serving as the intermediary between DNA and protein synthesis. Each option provided contains specific information about mRNA, but only option b is entirely accurate.
- Option a states, “mRNA includes a cap that consists of extra adenine nucleotides.” This is incorrect because the 5′ cap of mRNA is a modified guanine nucleotide (7-methylguanylate) rather than adenine nucleotides. The cap plays a vital role in protecting the mRNA from degradation and facilitating ribosome binding during translation.
- Option b is correct. After transcription, mRNA undergoes several processing steps in the nucleus, including the addition of the 5′ cap and poly-A tail, and the splicing of introns (non-coding regions). Once these modifications are complete, the mature mRNA exits the nucleus through the nuclear pores and enters the cytoplasm, where translation occurs.
- Option c claims, “mRNA is transcribed from DNA in the cytoplasm.” This statement is misleading because mRNA is transcribed in the nucleus. The transcription process involves RNA polymerase synthesizing mRNA from a DNA template, which occurs within the nuclear environment before the mRNA is transported to the cytoplasm.
- Option d suggests that “mRNA binds directly to amino acids during translation.” This is not accurate as well. While mRNA provides the coding sequence for amino acids, it does not directly bind to them. Instead, transfer RNA (tRNA) molecules carry specific amino acids to the ribosome, where they pair with the corresponding codons on the mRNA during translation.
In summary, mRNA is synthesized in the nucleus and subsequently processed before moving to the cytoplasm, where it serves as a template for protein synthesis.