Question
Biology Question on Regulation of Gene Expression
The sequence of structural genes in lac operon is
A
LacA,LacY,LacZ
B
LacA,LacZ,LacY
C
LacY,LacZ,LacA
D
LacZ,LacY,LacA
Answer
LacZ,LacY,LacA
Explanation
Solution
The lac operon consists of three structural genes (lacZ,lacXlacA). LacZ codes for β -galactosidase which hydrolyses lactose to glucose and galactose. LacY codes for lac permease, a membrane-bound protein constituent of the lactose transport system which increase permeability of the cell to β-galactosides. LacA codes of thiogalactoside transacetylase, an enzyme of uncertain metabolic function.