What complex is responsible for performing splicing in eukaryotic cells?

The spliceosome is a complex of proteins and RNA molecules that carries out the splicing process in eukaryotic cells. Splicing is crucial for the maturation of pre-messenger RNA (pre-mRNA), as it involves the removal of non-coding regions known as introns and the joining together of coding regions, or exons. This process allows for the production of a functional mRNA transcript that can be translated into a protein.

The spliceosome recognizes specific sequences at the intron-exon boundaries and catalyzes the splicing reaction. It is composed of small nuclear RNA (snRNA) and numerous associated proteins, collectively referred to as small nuclear ribonucleoproteins (snRNPs). This intricate assembly and the precise action of the spliceosome enable the complex regulation and diversity of gene expression seen in eukaryotic organisms, as alternative splicing can lead to different protein isoforms from a single gene.

In contrast, the other options like DNA polymerase and RNA polymerase are involved in DNA replication and transcription respectively, while the ribosome plays a role in protein synthesis. These functions, although essential to cellular processes, do not pertain to the splicing of RNA.