polar mutation

polar mutation

a MUTATION that affects expression not only of the GENE in which it occurs, but also of other genes that lie DOWNSTREAM in the same OPERON (see GENE EXPRESSION). A polar mutation exerts its effect by interfering with TRANSCRIPTION or TRANSLATION of the POLYCISTRONIC mRNA involved. A NONSENSE MUTATION located within a gene may be polar. TRANSPOSABLE GENETIC ELEMENTS carrying transcription and/or translation terminators can also produce polar mutations when they insert into genes.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005