Biotechnology and Genetic Technologies

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.

Key tools

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.

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