iGCSE Biology (0610)-21.2 Biotechnology - iGCSE Style Questions Paper 2

Question

The diagrams show the stages in the production of human insulin.

Which stage uses the enzyme DNA ligase?

▶️ Answer/Explanation

DNA ligase is a specific type of enzyme, often called “molecular glue,” that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. In the production of human insulin, restriction enzymes are used in Stages A and B to “cut” the DNA and the plasmid. In Stage C, the human insulin gene is mixed with the opened bacterial plasmid. DNA ligase is then required to chemically bond the sugar-phosphate backbones of the two DNA fragments, creating a single molecule of recombinant DNA. Without ligase, the insulin gene would not stay permanently attached to the vector. Stage D involves transformation and protein synthesis, which do not utilize ligase in this context.
✅ Answer: (C)

Question

Penicillin is produced in a fermenter by growing the fungus Penicillium. The graph shows how the mass of living Penicillium fungus and the concentration of penicillin change over time.

When is the best time to collect the penicillin?

A) at 1.5 days
B) at 3.0 days
C) at 3.5 days
D) at 5.0 days

▶️ Answer/Explanation

Solution

Ans: D

Penicillin is a secondary metabolite, meaning it is produced after the Penicillium fungus reaches the stationary phase of growth (when growth slows). The graph shows that penicillin concentration peaks at 5.0 days, while the fungal mass stabilizes. Earlier time points (A–C) represent active growth phases with lower penicillin yields. Thus, the optimal harvest time is D (5.0 days).

Question

The diagram shows some apparatus that was used to produce lactose-free milk.

The alginate beads do not react with any of the substances. X is an enzyme that catalyses a reaction involving one of the substances found in milk.

What are X and Y?

	X	Y
A	amylase	glucose
B	amylase	starch
C	lactase	glucose
D	lactase	starch

▶️ Answer/Explanation

Solution

Ans: C

To make lactose-free milk, lactase (X) breaks down lactose into glucose and galactose (Y would include glucose). Amylase (A/B) breaks down starch, which isn’t relevant here. The correct pair is C: lactase and glucose, as lactose is milk’s sugar.

iGCSE Biology (0610)-21.2 Biotechnology – iGCSE Style Questions Paper 2

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