Final answer:
Introns and exons play crucial roles in gene expression, with exons encoding proteins and introns being non-coding sequences. Alternative splicing can create diverse protein products from a single gene, contributing to biological complexity. Mutations and exon shuffling can lead to protein variability and evolution of new functions.
Step-by-step explanation:
The role of introns and exons is central in the process of gene expression in eukaryotic cells. Exons are the protein-coding sequences within a gene, whereas introns are the non-coding sequences that intervene between exons. During mRNA processing, introns are removed in a process called splicing. This splicing can vary, resulting in alternative splicing, which allows for multiple protein products to arise from a single gene. This variation in protein formation contributes to the complexity and adaptability of organisms.
Alternative splicing might evolve due to mutations in the splicing machinery or in the recognition sequences that signal the beginning and ending of introns. While errant splicing often results in nonfunctional proteins, at times it can result in the creation of functional protein variants. These new variants can then be subjected to natural selection. Additionally, mechanisms like exon shuffling through processes such as unequal crossover during meiosis can contribute to protein variability and evolutionary diversity, providing organisms with new functional proteins without losing the original ones.