In alternative splicing, the splicing a single primary RNA transcript occurs in two or more different but well defined patterns. In each splicing pattern, a defined set of exons is joined together to yield a functional mRNA molecule. The net effect of alternative splicing is the generation of a large number of different proteins from a relatively smaller number of genes.
If each human gene was alternatively processed to yield an average of 3 different proteins, the estimated 35,000 human genes would produce 105,000 different proteins. An extreme case of alternative processing is provided by the Drosophila gene Dscam.
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