Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following: a. operator
b. repressor
c. inducer
d. corepressor
e. promoter
f. positive regulation
g. allostery
h. negative regulation
i. attenuation

Answer and explanation:

The operator is a DNA fragment localized between the promoter and structural gene sequences that are able to repress operon transcription. A repressor is a molecule that binds to the operator to inhibit transcription, while an inducer is a molecule that activates transcription by binding either to the repressors or to the activators. A corepressor is a molecule that binds to repressors in order to activate them. A promoter is a DNA sequence localized upstream structural genes which binds to a transcription factor in order to activate operon transcription. Positive regulation is the process by which operon transcription acts as a positive loop, thereby increasing its own transcription, while negative regulation is the process by which operon transcription inhibits its own expression. Allostery refers to the process by which a molecule regulates operon transcription by binding to distal (and therefore non-functional) sites of the operon. Attenuation is a process able to reduce operon transcription and also to block subsequent translation.