Breeding & Engineering
Two ways humans reshape life: patient selective breeding over generations, and genetic engineering that inserts a gene overnight — plus the risks of each.
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Breeding & Engineering 🐕
Every breed of dog, every fat-eared crop of corn — none of them are natural. Humans made them, by choosing which organisms get to reproduce. This module compares the slow way (**selective breeding**) with the fast, precise way (**genetic engineering**) — and the risks of each.
Selective breeding 🌾
**Selective breeding** (artificial selection) is choosing which plants or animals reproduce, to get a desired characteristic — bigger crops, more milk, a gentle pet, disease resistance. It works with the **variation that already exists**, so it takes **many generations**.
How to selectively breed
An interactive activity.
The hidden cost ⚠️
Selective breeding has a downside. Repeatedly breeding from the same few individuals **reduces the gene pool** — the number of different alleles in the population falls. This **inbreeding** raises the chance of inheriting harmful genetic defects, and leaves the whole population with little variation — so a single new disease could wipe it out.
The danger
What is a genuine risk of selective breeding?
- It reduces variation (the gene pool), so inbreeding and disease become bigger threats
- It creates brand-new alleles that never existed
- It makes organisms evolve within one generation
- There are no risks at all
Genetic engineering 🧬
**Genetic engineering** changes an organism's genome directly, by **inserting a gene from another organism** to give a desired characteristic. Unlike selective breeding, it doesn't wait for generations — a **specific gene** is moved across in one step, even between completely different species.
How to engineer a gene
An interactive activity.
The delivery van
In genetic engineering, what is the job of a **vector** (such as a plasmid or virus)?
- To carry the desired gene into the cells of the target organism
- To cut the gene out of the DNA
- To make the organism grow faster
- To destroy the organism's own genes
In the real world 💉
Genetic engineering is already all around us: • **Bacteria** engineered to produce **human insulin** for people with diabetes. • **GM crops** — resistant to insects or disease, or giving bigger yields. But there are **concerns**: effects on wild flowers and insect populations, and uncertainty about long-term effects on human health.
The GM debate
An interactive activity.
Match the term
- Selective breeding
- Genetic engineering
- Vector
- Gene pool
- Choosing parents over many generations
- Inserting a specific gene from another organism
- Carries a gene into the target cells
- All the different alleles in a population
Tell them apart
What is the key difference between selective breeding and genetic engineering?
- Selective breeding selects from existing variation over generations; genetic engineering inserts a specific gene, immediately
- They are two names for the same process
- Genetic engineering happens naturally, breeding does not
- Both produce identical clones
In the exam 🎓
Reshaped. Grade-9 habits for this topic: • **Selective breeding** = choose desired parents → breed → select offspring → repeat over **generations**; risk = reduced **gene pool** / inbreeding. • **Genetic engineering** = **isolate** a gene → put it in a **vector** → **transfer** to the target; used for **insulin** and **GM crops**. • Keep them distinct: breeding **selects existing variation** slowly; engineering **inserts a specific gene** immediately.