An operon is a sequence of DNA that contains a cluster of genes under the control of a single Blank 1 Question 55[select: , operon, promoter, operator, repressor, positive, activator, genes] . Another key part of the operon regulatory sequence is the Blank 2 Question 55[select: , operon, promoter, operator, repressor, positive, activator, genes] . It can negatively regulate expression by binding a Blank 3 Question 55[select: , operon, promoter, operator, repressor, positive, activator, genes] . Conversely, positive regulation makes use of an enhancer sequence and Blank 4 Question 55[select: , operon, promoter, operator, repressor, positive, activator, genes] .多重下拉选择题