Fill in the Blanks with the Best Word or Phrase

Fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once.
$\begin{array}{lll}\text { allosteric } &\quad\quad\quad\quad\quad\quad\quad \text { negatively } & \text { positively } \\\text { constitutively } &\quad\quad\quad\quad\quad\quad\quad \text { operator } & \text { promoter } \\\text { induced } & \quad\quad\quad\quad\quad\quad\quad\text { operon } & \text { repressed }\end{array}$
The genes of a bacterial __________ are transcribed into a single mRNA.Many bacterial promoters contain a region known as a/an __________, to which a specific transcription regulator binds.Genes in which transcription is prevented are said to be __________.The interaction of small molecules, such as tryptophan, with __________ DNA-binding proteins, such as the tryptophan repressor, regulates bacterial genes.Genes that are being __________ expressed are being transcribed all the time.