Final answer:
Pre-mRNA splicing is the process that removes introns from the primary RNA transcript in nuclear genes. It is facilitated by spliceosomes composed of proteins and snRNAs. This process ensures the accurate removal of introns and the joining of exons to produce functional mRNA.
Step-by-step explanation:
Pre-mRNA splicing is the process that removes introns from the primary RNA transcript in nuclear genes. Introns are noncoding sequences that do not contribute to protein synthesis and must be removed to produce a functional mRNA molecule. The splicing process is facilitated by complexes called spliceosomes, which are composed of proteins and small nuclear RNAs (snRNAs). These spliceosomes recognize specific sequences at the 5' and 3' ends of introns and precisely remove them, then join the exons together to form a continuous mRNA transcript.