In: Biology
Ans: An operon is a cluster of structural genes that are transcribed into a polycisstronic mRNA whose protein products are involve in a common biochemical pathway. the expression of the structural genes is regulated by a common mechanisams. A typical operon consists of the following components.
1 Structural genes-polycistronic mRNA
2 Promoter- Cis regulater; Non-transcribed
3 Operator- Cis regulater; Non-transcribed
4 Regulatory gene-Monocistronicwith it own promoter ; trans acting
Example: the lac operon was the first ever operon to be studied; the operon concept was proposed by Jacob & monod for the regulation of the prokaryotes gene expression.
Lac operon contain 3 strictural genes Lac Z, Lac Y and Lac A which produce three genes Beta galactosidase, Beta galactoside permease and transacetylase enzymes respectively.
Beta galactosidase: Lac Z gene encodes the enzyme Beta galactosidase. Beta galactosidase carries out a two distinct functions. It hydrolyses the Betagalactoside lactose into galactose and glucose.
Beta galactoside permease: Lac Y encodes the enzyme Beta galactoside permease. it is a ttansmembranal carrier protein. whose function is to transport the lactose from the medium into the bacterial cytoplasm.
Transacetylase : Lac A encodes the enzyme transacetylase, whose function is to carryout the acetylation by using an acetyl group donor.