Question

Study the diagram given below that shows the steps involved in the procedure of selecting transformed bacteria and answer the questions that follow:

(a) Identify the colony that has got transformed. Justify your answer.   (0.5 + 0.5)

(b) What are the sites in a plasmid called where ampicillin and tetracycline resistance genes are inserted? State their role in genetic engineering.   (2)

(c) Name two enzymes playing an important role in genetic engineering.   (1)

OR

(c) State the role of β-galactosidase in insertional inactivation.   (1)

Answer 1

(a) Colony 4 is the recombinant transformant. It grows on Plate M (containing ampicillin) but fails to grow on Plate N (containing both ampicillin and tetracycline). This is because the insertion of foreign DNA into the tetracycline resistance gene disrupted it (insertional inactivation), rendering the colony sensitive to tetracycline while retaining its resistance to ampicillin.

(b) Selectable markers are locations where genes conferring resistance to ampicillin and tetracycline are integrated. They are crucial in genetic engineering as they facilitate the differentiation of transformants from non-transformants.

(c) EcoRI, Hind ill

OR

(c) β-galactosidase functions as a reporter enzyme. LacZ, a reporter gene, is responsible for its production. Insertional inactivation prevents the formation of B-galactosidase, resulting in a lack of blue colour. This results in white colonies of transformants.