Final answer:
Alternative RNA splicing is the process that enables a single gene to encode more than one polypeptide by varying combinations of exons and introns in the RNA transcript.
Step-by-step explanation:
The mechanism that allows a single gene to encode more than one polypeptide is alternative RNA splicing. This process is a form of post-transcriptional gene regulation in eukaryotes, wherein multiple protein products are produced by a single gene through different combinations of exons and introns in the RNA transcript. Alternative RNA splicing can occur in a regulated manner, with cell-controlled frequencies of splicing alternatives, allowing for various protein products in different cells or developmental stages. This process maintains the original 5'-3' exon order, even though combinations may vary, such as exons 1 2 4 5 6 7 or 1 2 3 6 7. Alternative splicing is common in human genes, with around 70 percent showing this behavior.