Define an operon. Giving an example, explain an Inducible operon.
A functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter is called an operon. An operon Is generally transcribed into polycistronic mRNA. A polycistronic mRNA is a single mRNA which codes for more than one protein. An operon Is made up of 3 basic DNA components:
(a) Promoter: A nucleotide sequence that enables a gene to be transcribed is called a promoter. It is recognised by RNA polymerase, which then initiates transcription.
(b) Operator: A segment of DNA to which a repressor binds is called an operator.
(c) Structural genes: The genes that are co-regulated by the operon are called structural genes.
Inducible Operon: When the operon is regulated by an Inducer. It is called an Inducible operon. An inducer can switch on or off the operon. Lac operon is an example of an inducible operon. Lactose Is a substrate of the enzyme beta-galactosidase and Is the Inducer of the lac operon.
In the presence of an inducer, the repressor becomes inactive. This allows transcription in the operator region, which results in the release of mRNA. Subsequently, mRNA promotes translation, and protein synthesis Is accomplished.