Zoology - Molecular Basis of Inheritance Question with Solution | TestHub
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
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Answer:
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) 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.
(ii) Lac Y (800 bp) : It codes for galactose permease enzyme which is a membrane bound protein and helps in transport of metabolites.
(iii) Lac A (800 bp) : It codes for galactose transacetylase an enzyme that transfers an acetyl group from acetyl Co-A to -galactosidase.
