Which statement correctly describes mRNA processing?

• A. Exons are cut out of the primary transcript, and the introns are spliced together.
• B. Introns are cut out of the primary transcript and spliced together at the end of the transcript.
• C. Exons are cut out of the primary transcript and transported to the endoplasmic reticulum.
• D. Introns are cut out of the primary transcript, and the resulting exons are spliced together.

Answer: (D)

Verified step by step guidance

1. Understand the structure of a primary mRNA transcript: It consists of exons and introns. Exons are coding regions, while introns are non-coding regions.
2. Recognize the purpose of mRNA processing: It is to remove non-coding sequences (introns) and join coding sequences (exons) to form a mature mRNA molecule that can be translated into a protein.
3. Identify the process of splicing: During mRNA processing, introns are removed from the primary transcript. This is done by a complex called the spliceosome.
4. Understand the role of exons: After introns are removed, the exons are spliced together to form a continuous sequence that will be translated into a protein.
5. Conclude with the correct description: Introns are cut out of the primary transcript, and the resulting exons are spliced together to form the mature mRNA.