Feeding the human race

Selective breeding

Humans choose parents with desired characteristics and breed them; over generations the trait becomes more common.

Steps:

1. Choose parents showing the desired feature (yield, disease resistance, gentle temperament).
2. Cross them.
3. Select the best offspring; breed those.
4. Repeat over many generations.

Examples: high-yield wheat, cattle with high milk yield, dogs bred for behaviour.

Risk: reduces genetic variation → entire population vulnerable to a new disease (e.g. Irish potato famine).

Genetic engineering

Transfers a useful gene from one organism into another's genome.

Steps (the OCR mark-scheme order):

1. Identify and isolate the useful gene using restriction enzymes.
2. Insert the gene into a vector (often a plasmid or virus) using ligase.
3. Transfer the vector into the target cell.
4. The cell expresses the new gene.

Examples: bacteria producing human insulin, golden rice (vitamin-A-rich), Bt-cotton resistant to insect pests, sheep producing therapeutic proteins in milk.

Concerns: ethical (playing God, animal welfare), ecological (gene transfer to wild relatives), economic (patents on seed).

Food security

Defined as having enough safe, nutritious food for an active healthy life. Threats:

• Rising population.
• Climate change reducing yields.
• New pests and pathogens.
• Cost of agricultural inputs (fertilisers, fuel).
• Conflict.

Solutions: selective breeding, GE crops, sustainable fisheries with quotas, hydroponics and indoor farming, reduced food waste.

Biotechnology — mycoprotein

The fungus Fusarium is grown in large vessels (fermenters) on a glucose syrup with ammonia, vitamins and oxygen, at controlled pH and temperature. The biomass is harvested and processed into Quorn — a protein-rich meat alternative.

OCR exam tip

In a 4-mark "describe genetic engineering" answer, put the four steps in process order (isolate → insert → transfer → express). Bullet, in order, no fluff.