The process by which the primary RNA transcript from a gene is processed differently to yield several mRNA species. Specifically, a gene is normally transcribed into RNA containing both exon and intron sequences; the introns are then removed, leaving only the coding exon regions. During alternative splicing, some exons are skipped over and removed together with the introns. Since many exons code for a module of protein, alternative splicing leads to the generation of several related proteins from a single gene. Alternative splicing may be tissue or disease specific.

Various ways of splicing out introns in eukaryotic pre-mRNAs resulting in one gene producing several different mRNAs and protein products.

Splicing is a post-transcriptional modification that occurs in messenger RNA (mRNA), the template that is used to create a protein from a gene. Splicing refers to the enzymatic cutting of mRNA at specific recognition sites between exons (DNA segments needed to code for proteins) and introns (DNA not used to make proteins). Splicing removes the RNA that will not be used in the translation of a protein. The pieces left are joined together by the splicing machinery and introduced into the translation machinery that creates proteins. mRNA can have numerous splice recognition sites, and alternative splicing occurs when the splicing machinery excises material from different splice sites in the mRNA strand. When these alternatively spliced mRNAs are translated, the proteins produced are related, but have sequence variations. Mutations that affect protein function and stability can sometimes be attributed to mutations in splice recognition sites. See also Translation.