Final answer:
About 70 percent of human genes are expressed as multiple proteins through alternative splicing, a process which increases protein diversity and plays a vital role in gene regulation. This mechanism allows a single gene to generate various protein isoforms by piecing together different combinations of exons and introns.
Step-by-step explanation:
Alternative splicing is a regulated process during gene expression that allows a single gene to code for multiple proteins. In humans, it is estimated that about 70 percent of genes are expressed as multiple proteins through this process. Not only does alternative splicing contribute to protein diversity, but it also plays an essential role in gene regulation. Although every exon in a transcript maintains its original 5'-3' order, different combinations of exons and sometimes introns are pieced together to create unique mRNA transcripts. These transcripts can then be translated into distinct protein isoforms, serving various functions in the cell. With over 95% of multi-exon genes in humans undergoing alternative splicing, it's a cornerstone for biological complexity and an economy of genes, meaning that a vast array of proteins can be produced without the need for a proportional increase in gene number.