# Biotechnology and Genetic Technologies

> Selective breeding, recombinant DNA, PCR and gel electrophoresis, transgenic organisms, gene editing with CRISPR and cloning.

From HSC Biology on WhizzNotes, free study notes for NSW students: https://whizznotes.com/biology/biotechnology/. Updated 3 November 2026.
Year 11 and Year 12 boxes go deeper than the Year 10 text around them.

### Story time: Rice that fights blindness
Hundreds of thousands of children around the world go blind each year because their diet is low in vitamin A. Many of them eat mostly white rice, which has none.

Scientists took a gene from a daffodil and a gene from a soil bacterium and put them into rice. The new rice makes beta-carotene, which the body turns into vitamin A. Its grains are golden yellow, so it is called **Golden Rice**. In 2021 the Philippines became the first country to approve it for farmers to grow. It is a crop made by moving genes between species that could never breed together.

**In short:** Biotechnology uses living things or their parts to make useful products. Genetic technologies include recombinant DNA (cutting and joining genes into plasmids), PCR to copy DNA, CRISPR-Cas9 to edit genes, and cloning to make identical copies, each with benefits, risks and ethical issues.

## Starting point: what you already know

- DNA is made of bases, and the genetic code is universal (see From DNA to Protein).
- PCR copies DNA and gel electrophoresis sorts it by size (see Genetic Variation in Populations).
- Asexual reproduction makes clones (see Reproduction).

## What is biotechnology?

**Biotechnology** is using living things or their parts to make products or solve problems. People have done it for thousands of years: brewing beer, baking bread and breeding animals. Modern biotechnology changes DNA directly.

## Selective breeding (old technology)

Humans choose parents with wanted features and breed them, generation after generation. Merino sheep were bred in Australia for fine wool. Wheat varieties were bred to resist rust and drought. Dogs were bred from wolves into hundreds of breeds.

It is slow and limited to features already in the species. It also lowers **genetic diversity**.

## Recombinant DNA: making transgenic organisms

**Recombinant DNA** is DNA joined from two different sources. A **transgenic organism** (a genetically modified organism, or GMO) has a gene from another species.

### Worked example: Making human insulin in bacteria
1. **Cut**: a **restriction enzyme** cuts the human insulin gene out of DNA at a specific base sequence, leaving "sticky ends".
2. The same enzyme cuts open a bacterial **plasmid** (a small loop of DNA), giving matching sticky ends.
3. **Join**: **DNA ligase** joins the insulin gene into the plasmid. This is recombinant DNA.
4. **Insert**: the plasmid is put back into bacteria.
5. **Grow**: the bacteria multiply in huge tanks and make human insulin, which is purified for people with diabetes.

Before 1982, insulin came from the pancreases of pigs and cows.

## Key tools

| Tool | Job |
|---|---|
| **Restriction enzymes** | Cut DNA at specific sequences ("molecular scissors") |
| **DNA ligase** | Joins DNA pieces ("molecular glue") |
| **Plasmids and viruses** | **Vectors** that carry genes into cells |
| **PCR** | Makes millions of copies of a DNA section |
| **Gel electrophoresis** | Separates DNA pieces by size |
| **CRISPR-Cas9** | Edits a gene at an exact spot |

## PCR step by step

The **polymerase chain reaction** copies DNA in a machine that changes temperature in cycles.

1. **Denature** at about 95 degrees: the strands separate.
2. **Anneal** at about 55 degrees: short **primers** attach to each side of the target.
3. **Extend** at about 72 degrees: heat-resistant **Taq polymerase** builds new strands.

Each cycle doubles the DNA. After 30 cycles, one copy becomes $2^{30}$, over a billion copies.

## CRISPR gene editing

**CRISPR-Cas9** comes from a defence system in bacteria. A **guide RNA** matches the target gene and leads the **Cas9** enzyme there. Cas9 cuts both strands, and the cell repairs the cut, either switching the gene off or pasting in a new sequence. It is fast, cheap and precise, and its discoverers won the 2020 Nobel Prize in Chemistry.

## Cloning

- **Plant cloning**: cuttings and **tissue culture**, growing whole plants from a few cells on agar.
- **Animal cloning**: **somatic cell nuclear transfer**. The nucleus from a body cell goes into an egg with its nucleus removed. The egg develops into an animal identical to the nucleus donor. Dolly the sheep (1996) was the first mammal cloned this way.

**Mind map**

```text
Biotechnology
  Old
    Brewing and baking
    Selective breeding
  Recombinant DNA
    Cut: restriction enzymes
    Join: DNA ligase
    Carry: plasmid vectors
    Insulin from bacteria
  Tools
    PCR copies
    Gel sorts
    CRISPR edits
  Cloning
    Cuttings, tissue culture
    Nuclear transfer: Dolly
  Transgenic examples
    Golden Rice
    Bt cotton
```

### Year 11: Transgenic crops in Australia
**Bt cotton** has a gene from the bacterium *Bacillus thuringiensis* that makes a protein toxic to caterpillar pests. Since it was introduced, Australian cotton farmers have cut insecticide spraying by around 85%. Most Australian cotton is now GM. Some canola is also GM, engineered to resist herbicides.

Every GM crop in Australia must be approved by the Office of the Gene Technology Regulator, and GM foods must be labelled.

**Agrobacterium.** This soil bacterium naturally moves part of its plasmid into plant cells. Scientists put the wanted gene into its plasmid, let it infect plant cells, then grow whole transgenic plants from those cells by tissue culture.

**Marker genes.** Plasmids often carry an **antibiotic resistance gene** too. After the step that inserts the plasmid, the bacteria are grown with the antibiotic: only those that took up the plasmid survive.

**Gene cloning versus organism cloning.** Gene cloning makes many copies of one gene (in bacteria or by PCR). Organism cloning makes a whole new individual identical to another.

### Year 12: Evaluating biotechnology for the HSC
HSC questions ask you to evaluate the **benefits**, **risks** and **ethics** of a technology, and its effect on **biodiversity**.

| | Benefits | Concerns |
|---|---|---|
| Agriculture | Higher yields, less pesticide, crops for drought and salty soil | Fewer varieties grown, so lower genetic diversity. Genes may spread to wild relatives. Pests may evolve resistance |
| Medicine | Insulin, vaccines, gene therapy, faster diagnosis | Cost and access. Germline editing could be passed to future generations |
| Society | Better nutrition, less land cleared | Ownership of seeds and patents by large companies. Consent and fairness |

**Biodiversity link.** Biotechnology can **reduce** biodiversity when farmers plant large areas of one clone or one GM variety. It can also **help**: DNA analysis guides breeding of endangered species, and gene drives are being researched to control pests like cane toads and invasive mice.

Always give **both** sides and finish with a supported judgement.

**Why PCR levels off.** After about 30 cycles the primers and free nucleotides start to run out, and the polymerase slowly wears out, so copies stop doubling.

**Reading STR results.** A child with repeats 16 and 18 and a mother with 15 and 16 got 16 from the mother. The 18 must come from the father, so only a man with an 18 repeat could be the father.

**Why start from mRNA?** Human genes contain introns, and bacteria cannot cut them out. Using **reverse transcriptase** to copy insulin mRNA back into DNA gives a gene with no introns, which bacteria can read.

**Cutting a circle.** A restriction enzyme that cuts a **circular** plasmid at two sites makes **two** fragments. (A straight piece of DNA cut at two sites makes three.)

**Somatic versus germline editing.** Somatic gene therapy changes body cells, so only the patient is affected. Germline editing changes eggs, sperm or embryos, so the change passes to future generations.

## Quick summary

- Biotechnology uses living things to make products. Selective breeding is an old form.
- Recombinant DNA: restriction enzymes cut, DNA ligase joins, plasmids carry genes into cells.
- Transgenic organisms have genes from another species: insulin-making bacteria, Golden Rice, Bt cotton.
- PCR copies DNA (denature, anneal, extend). CRISPR-Cas9 edits genes precisely.
- Cloning makes identical copies: cuttings, tissue culture, nuclear transfer.
- Biotechnology has benefits, risks and ethical issues, including effects on genetic diversity.

## Quiz

Try these questions from the chapter quiz.

1. Which enzyme cuts DNA at a specific base sequence?
   - A. Restriction enzyme
   - B. DNA ligase
   - C. Amylase
   - D. RNA polymerase
   - Answer: A. Restriction enzyme. Restriction enzymes are molecular scissors.

2. Which enzyme joins pieces of DNA?
   - A. Helicase
   - B. DNA ligase
   - C. Restriction enzyme
   - D. Protease
   - Answer: B. DNA ligase. Ligase is molecular glue.

3. A small loop of bacterial DNA used to carry a gene is a
   - A. chromosome
   - B. plasmid
   - C. ribosome
   - D. primer
   - Answer: B. plasmid. Plasmids are common vectors.

The whole chapter quiz is on the page, for signed-in students: https://whizznotes.com/biology/biotechnology/#quiz