NEET2007ZoologyMolecular Basis of InheritanceActual
E. coli cells with a mutated Z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because
Options
- Ain the presence of glucose, E. coli cells do not utilize lactose
- Bthey cannot transport lactose from the medium into the cell
- Cthe lac operon is constitutively active in these cells
- Dthey cannot synthesize functional -galactosidase
Correct answer
D. they cannot synthesize functional -galactosidase
Step-by-step solution
Lac operon is a cluster of genes encoding three proteins that bacteria use to obtain energy from the sugar lactose. There are three structural genes in lac operon. Promoter for lac i (i) Lac Z (3063 bp) : This gene codes for the enzyme galactosidase which breaks lactose into glucose and galactose to be utilized in the cell. Therefore, E.coli cells with a mutated Z genes of the lac operon can not grow in medium containing only lactose as the source of energy because they cannot synthesize functional -galactosidase.