There are five different types of alternative splicing: exon skipping, constitutive splicing, mutually exclusive splicing , alternative 3’ or 5’ splice site, and intron retention.

• Exon skipping is when an exon is spliced out of the primary RNA strand or kept; this is the most common type of alternative splicing.
• Constitutive splicing is the process of removing introns from pre-mRNA and sticking the exons together to form a mature mRNA.
• Mutually exclusive splicing is a type of splicing in which only one of two or more potential exons is spliced into the mature mRNA. 
• The alternative 3’ splice acceptor site is used to change the 5’ downstream exon. The alternative 5’ splice donor site is used to change the 3’ upstream exon.
• Intron retention is an alternative splicing mode whereby introns are spliced out as an intron or retained in mature mRNAs.