Final answer:
Exon shuffling, especially occurring in eukaryotic genes, is facilitated by transposons like helitrons and LINEs; it contributes to species diversity by enabling genes to exchange exons and create proteins with novel functions.
Step-by-step explanation:
Exon Shuffling
Exon shuffling is a molecular mechanism that plays a critical role in the evolution and diversity of eukaryotic organisms. Particularly in eukaryotic genes, which are segmented into exons and introns, exon shuffling can occur mainly due to the actions of transposons and unequal recombination during meiosis. Introns serve as a buffer against mutations and as potential zones for the rearrangement of genetic material, including the shuffling of exons. Helitrons and LINE transposition are different mechanisms through which exon shuffling can occur, leading to the insertion of new exon-encoded domains and diversification of gene functions.
Consider the case of the tissue plasminogen activator (TPA), which shares domains with the gene for epidermal growth factor (EGF), illustrating how exon shuffling contributes to the emergence of new, functionally diverse proteins. This process increases species diversity by allowing genes to acquire or lose exons, thereby producing proteins with new structural domains and functions.