Which of the following is true of RNA processing? (A) Exons are cut out before mRNA leaves the nucleus. (B) Nucleotides are added at both ends of the RNA. (C) Ribozymes may function in the addition of a 5′ cap. (D) RNA splicing adds a poly-A tail to the mRNA.

Verified step by step guidance

1. Identify the correct statements about RNA processing, which involves modifications to the pre-mRNA transcript in eukaryotic cells.
2. Understand that exons are the coding regions of the RNA that remain in the sequence to be expressed, while introns are the non-coding regions that are removed during RNA splicing.
3. Recognize that a 5′ cap is added to the 5′ end of the RNA and a poly-A tail is added to the 3′ end, but these modifications involve specific enzymes rather than ribozymes.
4. Recall that RNA splicing involves the removal of introns and the joining of exons, and does not add a poly-A tail to the mRNA.
5. Evaluate each option based on the known processes of RNA processing: splicing, 5′ capping, and poly-A tail addition.

Key Concepts

RNA Processing

RNA processing refers to the modifications that pre-mRNA undergoes before it becomes mature mRNA. This includes the removal of non-coding sequences called introns and the joining together of coding sequences known as exons. Additionally, RNA processing involves the addition of a 5' cap and a poly-A tail, which are crucial for mRNA stability and translation.

Exons and Introns

Exons are the coding regions of a gene that are retained in the final mRNA product, while introns are non-coding regions that are removed during RNA splicing. Understanding the distinction between exons and introns is essential for grasping how mRNA is prepared for translation, as only exons contribute to the protein-coding sequence.

5' Cap and Poly-A Tail

The 5' cap is a modified guanine nucleotide added to the beginning of the mRNA transcript, which protects the mRNA from degradation and assists in ribosome binding during translation. The poly-A tail, a sequence of adenine nucleotides added to the 3' end, also enhances mRNA stability and regulates its translation efficiency. Both modifications are critical for the proper functioning of mRNA in protein synthesis.