This guide covers IGCSE Biology topic 20: biotechnology and genetic engineering. You will revise fermentation (yeast, bacteria; bread, yogurt, biogas), genetic engineering (cut and paste genes; insulin; GM crops), and the benefits and risks of GM.

Key concepts to revise

• Fermentation – Yeast: anaerobic respiration → ethanol + CO₂ (bread, beer). Bacteria: e.g. lactose → lactic acid (yogurt). Biogas: methane from decay.
• Genetic engineering – Gene cut from one organism (e.g. human insulin gene); inserted into another (e.g. bacterium); organism makes the protein (e.g. insulin).
• GM crops – Genes inserted for pest resistance, herbicide resistance, or improved nutrition. Benefits: higher yield; risks: unknown long-term effects, effect on wildlife.
• Insulin – Produced by bacteria with human insulin gene; used by diabetics; no animal source.

Exam tips and command words

• State – What fermentation is (anaerobic breakdown; yeast/bacteria); what genetic engineering is (transfer of genes between organisms).
• Describe – The steps of genetic engineering (identify gene → cut → insert into vector → insert into host → host expresses gene).
• Explain – Why bacteria are used for insulin production (rapid reproduction; human gene inserted; produce human insulin).
• Discuss – Benefits and risks of GM crops (one of each).

Common mistakes

• Saying genetic engineering “changes the organism’s DNA” without specifying that a specific gene is transferred.
• Confusing fermentation (anaerobic; yeast/bacteria) with respiration (aerobic in mitochondria).
• Not stating that insulin from genetic engineering is identical to human insulin (reduces allergy risk).

Revision checklist

• Describe fermentation in yeast (glucose → ethanol + CO₂) and one use (bread or beer).
• Describe the main steps of genetic engineering (gene cut, inserted, expressed).
• Explain how human insulin is produced using bacteria.
• State one benefit and one risk of GM crops.

Next steps

Book a free trial with an IGCSE Biology tutor to practise biotechnology and genetic engineering questions, or explore Tutopiya’s learning portal for more revision resources.

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