Final answer:
Splicing is the complex process that removes introns from a pre-mRNA molecule before protein synthesis.
Step-by-step explanation:
The complex process that removes introns from a pre-mRNA molecule is called splicing. Splicing ensures that introns, noncoding regions of the pre-mRNA, are completely and accurately removed before protein synthesis. This process is conducted by protein complexes called spliceosomes, which recognize specific sequences at the 5' and 3' ends of the introns.