The introns found in eukaryotic pre-mRNA are removed by a large complex called the:

• A. ribosome
• B. spliceosome
• C. exosome
• D. proteasome

Answer: (B)

Verified step by step guidance

1. Understand that introns are non-coding sequences within eukaryotic pre-mRNA that need to be removed before translation.
2. Recall that the removal of introns is a process called RNA splicing, which occurs in the nucleus of eukaryotic cells.
3. Identify the molecular machinery responsible for splicing; it is a large complex made up of proteins and small nuclear RNAs (snRNAs).
4. Recognize that this complex is called the spliceosome, which precisely removes introns and joins exons together.
5. Differentiate the spliceosome from other complexes: the ribosome synthesizes proteins, the exosome degrades RNA, and the proteasome degrades proteins.