Protein isoform

In genetics, an isoform is a member of a set of similar products that originate from the same gene; such a set can consist of mRNAs or their resultant proteins. The best-studied isoforms are the protein isoforms, or "protein variants", resulting from differences in the coding DNA sequences (CDS) of their precursor mRNAs. While many perform the same or similar biological roles, some protein isoforms have unique functions. A set of protein isoforms may be formed from alternative splicings, variable promoter/transcription start site (TSS) usage, or other post-transcriptional modifications of a single gene; post-translational modifications are generally not considered. (For that, see Proteoforms.) Through RNA splicing mechanisms, mRNA has the ability to select different protein-coding segments (exons) of a gene, or even different parts of exons from RNA to form different mRNA sequences. Each unique sequence produces a specific form of a protein.