Fig. 3.1 is a diagram of the lac operon and an adjacent region of the E. coli genome. Name sections 1, 2, 3 and 4 shown in Fig. 3.1.
Some enzymes must be present inside E. coli for it to take in and use lactose. When the lac operon genes are expressed, the enzymes β-galactosidase and lactose permease are made in large amounts. Outline the functions of β-galactosidase and lactose permease.
Gene $I$ lies a short distance from the lac operon. The product of gene $I$, a repressor protein, is a constitutive protein. State what is meant by the term constitutive protein.
Explain why the structural genes of the lac operon are not expressed when lactose is absent.
A strain of E. coli has been produced with a mutation in gene $I$. Expression of this gene gives a non-functional repressor protein. Suggest a negative effect that this mutation will have on this strain of E. coli.