Figure 1. Alternative splicing.

The splicing process removes introns from primary RNA and concatenates exons to generate mature mRNAs. Exons can be included or skipped, thus generating alternatively spliced products that encode different proteins (light gray). The example shows how spliced products could differ by the presence or absence of a domain that interacts with another protein (dark gray). Regulatory sequences in the exons or introns promote (orange) or prevent (blue) inclusion of the alternative exon. Nucleotide differences (e.g., A or C) can alter the function of the regulatory sequences and therefore change the balance between alternatively spliced mRNAs.