A) The lac operon is constitutively active in these cells.
B) They cannot synthesise functional beta- galactosidase.
C) In the presence of glucose, \[E.coli\]cells do not utilise lactose.
D) They cannot transport lactose from the medium into the cell.
Correct Answer: B
Solution :
Operons are segments of genetic material which function as regulated unit or units that can be switched on and switched off. An operon consists of one to several structural genes (Three in lac operon). These are the genes which produce mRNAs for forming polypeptides/proteins/enzymes. \[lac\text{ }z\]Produces enzyme \[\beta \]galactosidase for splitting lactose into glucose and galactosidase. \[lac\text{ }y\]Produces enzyme galactoside permease required for the entry of lactose, lac a produces enzyme thiogalactoside transacetylase. The three structural genes of the operon produce a single polycistronic mRNA. Hence mutated \[z\]gene cannot grow in medium containing only lactose as the source of energy.
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