A directed change in translational reading frames that allows the production of a single protein from two or more overlapping genes. The process's programmed by the nucleotide sequence of the mRNA and's sometimes also affected by the secondary or tertiary mRNA structure. It's been described mainly in viruses (especially retroviruses; retrotransposons; and bacterial insertion elements but also in some cellular genes. Notably the p19 tumor suppressor gene in humans encodes a frameshift.… (More on Frameshift)