Sentence:  That segment of DNA, which is bounded on the codogenic strand by a promotor and in the 5' direction from the promotor by a terminator, defines a <WSD>scripton</WSD>. A <WSD>scripton</WSD> beginning with a given promotor may vary in length through activation or inactivation of differently located terminators. 
Meaning of the word marked with <WSD> tags:  (molecular biology) A segment of DNA or RNA that is under the control of a single autonomous promotor. A single scripton may encode multiple cistrons involving separate terminators.