AQA GCSE Biology Biology Paper 2 (Foundation), June 2024: Question 3

✅ Correct Answers

03.1: Gene (for antigen)
Also accepted: DNA for antigen / allele for antigen.

03.2: (Pure) antigen(s)

💡 Key Knowledge

• Genes carry instructions: In genetic engineering, a specific gene (a section of DNA) is isolated from a donor and inserted into a vector or host cell.
• Expression: The host cell (yeast) reads the viral gene and uses its own ribosomes to manufacture the foreign protein (the antigen).

🧠 Exam Technique

When a question states "Use information from Figure 3", look carefully at the arrow labels:

• The arrow pointing into the yeast points from "Gene for antigen".
• The arrow showing what the yeast produces points to "Antigen".

❌ Common Errors

• 03.1: Writing just "DNA" or "allele" without qualification was rejected by examiners. It must be specified as the gene for the antigen.
• Writing "nucleus" or "whole virus" for what is inserted into the yeast cell.

✅ Correct Answer

Tick Box 2: "The viruses may cause an infection."

💡 Key Knowledge

Older vaccines used weakened (attenuated) or heat-inactivated whole viruses. If the heat-treatment process is incomplete or ineffective, live viral particles remain capable of replicating and causing disease in the patient.

By contrast, genetically engineered subunit vaccines (like the yeast method shown) contain only pure antigens (proteins), never whole pathogens, making an infection impossible.

❌ Common Errors

• Ticking "The viruses may be inactive" — Inactivity is the goal of heat treatment, not the danger!
• Ticking "The viruses will not mutate" — Lack of mutation is not why a vaccine is dangerous.

✅ Correct Answers (Choose any three)

• Light / sunlight
• Water / rain / soil moisture
• Mineral ions / salts / minerals (or specific named ions, e.g. nitrates, magnesium, phosphates)
• Space (or room to grow)
• Oxygen in the soil (for root respiration)

💡 Key Knowledge: Plants vs. Animals

Be very careful not to confuse what plants compete for with what animals compete for:

• Plants compete for: Light, space, water, and mineral ions from the soil.
• Animals compete for: Food, mates, and territory.

❌ Common Errors & Mark Traps

• "Food" or "Nutrients": Plants make their own food by photosynthesis! Examiners explicitly reject "food" and "nutrients".
• "Carbon dioxide": CO₂ is abundant in the open atmosphere and is generally not considered a limiting competitive factor in open fields.
• "Sun": Too vague; you must specify sunlight or light.

✅ 03.5 Advantage (Any one)

• Crop plants grow better / grow larger
• Crop plants have a higher yield / produce more maize

Note: The question already explains weeds are killed, so saying "it kills weeds" or just "less competition" without linking to crop growth was not credited.

✅ 03.6 Problem (Any one)

• May kill / harm / poison other (non-target) plants or wild flowers
• May pollute / contaminate streams, rivers, or soil
• May kill / harm / poison animals, insects, or humans
• May reduce biodiversity / disrupt food chains
• May alter the taste of the GM maize

🧠 Exam Technique: Follow Restrictions

• Read the bold condition: Question 03.6 explicitly states: "Do not refer to cost in your answer." Any mention of herbicide cost, seed expense, or farmer profit immediately scores 0 marks.
• Be specific about harm: Avoid writing "it is poisonous" on its own. State what it harms (e.g. harmless insects, hedgerow wildflowers, aquatic life).

❌ Common Misconceptions

• Confusing herbicide (weed killer) with insecticide / pesticide. Glyphosate kills unwanted plants.
• Stating that the GM maize itself will be killed by the weed killer (the prompt states it is resistant to glyphosate).