What is the primary difference between introns and exons in eukaryotic RNA processing?

• A. Introns are sequences that are translated into proteins, while exons are sequences that are transcribed but not translated.
• B. Introns are coding sequences that are expressed, while exons are non-coding sequences that are removed during RNA splicing.
• C. Introns are sequences that remain in the final mRNA, while exons are sequences that are spliced out.
• D. Introns are non-coding sequences that are removed during RNA splicing, while exons are coding sequences that are expressed.

Answer: (D)

Verified step by step guidance

1. Understand the context of RNA processing in eukaryotic cells, which involves the modification of pre-mRNA to form mature mRNA.
2. Recognize that introns and exons are parts of the pre-mRNA. Introns are non-coding sequences, while exons are coding sequences.
3. During RNA splicing, introns are removed from the pre-mRNA, and exons are joined together to form the final mRNA sequence.
4. Exons are the sequences that remain in the mRNA and are translated into proteins, whereas introns do not contribute to the protein sequence.
5. The primary difference is that introns are non-coding sequences removed during RNA splicing, while exons are coding sequences that are expressed in the final protein product.