Editing Rho factor (section)

== Mutations ==

A [[nonsense mutation]] in one gene of an [[operon]] prevents the translation of subsequent genes in the unit. This effect is called mutational polarity. A common cause is the absence of the [[messenger RNA|mRNA]] corresponding to the subsequent (distal) parts of the unit. Suppose that there are Rho-dependent terminators within the transcription unit, that is, before the terminator that usually is used. Normally these earlier terminators are not used, because the [[ribosome]] prevents Rho from reaching RNA polymerase. But a nonsense mutation releases the ribosome, so that Rho is free to attach to and/or move along the RNA, enabling it to act on RNA polymerase at the terminator. As a result, the enzyme is released, and the distal regions of the transcription unit are never transcribed.{{Citation needed|date=July 2019}}