frameshift

Translational frameshifting or ribosomal frameshifting refers to an alternative process of protein translation. A protein is translated from one end of the mRNA to the other, from the 5' to the 3' end. Normally a protein is translated from a template mRNA with consecutive blocks of 3 nucleotides being read as single amino acids. However, certain organisms may exhibit a change or shift in the ribosomes frame by one or two nucleotides when translating the genetic code. This is deemed translational or ribosomal frameshifting. The process can be programmed by the nucleotide sequence of the mRNA and is sometimes affected by the secondary or tertiary mRNA structure. It has been described mainly in viruses (especially retroviruses), retrotransposons and bacterial insertion elements, and also in some cellular genes.