The bacterium $Escherichia\ coli$ can metabolise glucose or disaccharides such as lactose. Lactose must first be hydrolysed by the enzyme $\beta$-galactosidase, producing glucose and galactose, and these can then be used by $E.\ coli$. Production of $\beta$-galactosidase is regulated by a DNA sequence known as the $lac$ operon.
(a)[2]
On Fig. 7.2, indicate where RNA polymerase and the repressor molecule are located when lactose is present.
(b(i))[1]
Name the category of gene that $lacY$ represents.
(b(ii))[2]
Name the protein product encoded by $lacY$ and state the precise function of this protein.
(c)[4]
Describe the population growth curve shown in Fig. 7.3 and suggest reasons for it.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “RNA polymerase binds to promoter” …