Question

What is an Inducible Operon?

Answer 1

In genetics, an operon is a functional unit of DNA that contains a cluster of genes controlled by a single promoter. The genes are transcribed into a single strand of mRNA and either translated together in the cytoplasm or spliced to produce monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product.

Complete answer:
Originally, operons were thought to exist only in prokaryotes (organelles derived from bacteria such as plastids), but since the discovery of the first operons in eukaryotes in the early 1990s, more evidence has emerged suggesting they are more common than previously assumed. In general, prokaryotic operons generate polycistronic mRNAs, whereas eukaryotic operons generate monocistronic mRNAs.Some operons are normally "off," but a small molecule can turn them "on." The molecule is known as an inducer, and the operon is known as inducible.

The lac operon, for example, is an inducible operon that encodes enzymes for the metabolism of sugar lactose. It only activates when the sugar lactose is present (and other, preferred sugars are absent). Allolactose, a modified form of lactose, is the inducer in this case.

Thus, An inducible operon is normally turned off and is involved in the nutrient breakdown (catabolic pathways). Lac operons are an example of inducible operons.

Note: In the absence of lactose, the lac repressor binds to the lac operon's operator region, preventing RNA polymerase from transcribing the structural genes. When lactose is present, however, the lactose within the cell is converted to allolactose. Allolactose acts as an inducer molecule, binding to the repressor and causing it to change shape, rendering it unable to bind to the operator DNA. When the repressor is removed in the presence of lactose, RNA polymerase can move through the operator region and start transcription of the lac structural genes.