Genetic Engineering and Cloning: KS3 Biology Guide

Genetic engineering is the deliberate modification of an organism's DNA to introduce new traits or alter existing ones. Scientists can remove a gene from one species and insert it into another, creating genetically modified organisms (GMOs) with useful characteristics such as pest resistance, higher yield, or the ability to produce human insulin.

What is a gene and how does genetic engineering work?

Start at the largest scale: an organism — a bacterium, a rice plant, a human — is determined by the proteins its cells produce. Zoom in to the organ level: the pancreas secretes insulin; zoom further to the cell: beta cells translate a genetic instruction into insulin protein; zoom to the molecule: that instruction is a segment of DNA called a gene.

A gene is a section of DNA that codes for making one specific protein. Genetic engineering cuts a desired gene from one organism's DNA and inserts it into another, so the recipient can manufacture the protein the gene encodes.

The key molecular tools (simplified for KS3):

Restriction enzymes — molecular "scissors" that cut DNA at specific recognition sequences, leaving short single-stranded overhangs called sticky ends.

Ligase — a "glue" enzyme that joins DNA strands together, sealing the new gene into the host DNA.

Vector — a carrier that transports the gene into the host cell. The most common vector at KS3 is a bacterial plasmid: a small, circular piece of DNA found in bacteria, separate from their main chromosome.

At the molecular scale, what scientists are doing is editing the instruction manual written in the DNA — cutting out one line of code from one manual and pasting it into a completely different set of instructions. The recipient cell then follows those new instructions and manufactures the protein accordingly.

What are examples of genetically modified organisms?

GMO | Gene inserted | Where gene from | Benefit
GM bacteria (e.g. E. coli) | Human insulin gene | Human pancreatic cells | Produce human insulin for diabetics; cheaper and purer than pig-derived insulin
Bt cotton/maize | Cry gene (insecticidal protein) | Bacillus thuringiensis bacteria | Plant produces its own insecticide; reduces pesticide use
Golden Rice | Beta-carotene synthesis genes | Maize and soil bacteria | Rice produces vitamin A precursor; could reduce vitamin A deficiency in developing countries
GM salmon (AquAdvantage) | Growth hormone gene | Chinook salmon + ocean pout | Grows twice as fast; reaches market size in half the time
Herbicide-resistant soybeans | Herbicide resistance gene | Bacteria | Survives herbicide spraying; simplifies weed control
GM sheep / goats | Human protein genes | Humans | Produce human proteins (e.g. clotting factors) in their milk for medical use

How is human insulin produced using genetic engineering?

The production of human insulin by GM bacteria is one of the clearest and most examined examples of genetic engineering in UK secondary science.

Identify the human gene that codes for insulin, located on chromosome 11.

Use restriction enzymes to cut the insulin gene from a human DNA strand, producing sticky ends.

Cut a bacterial plasmid with the same restriction enzyme, producing complementary sticky ends.

Mix the insulin gene with the cut plasmid; ligase enzyme joins them together, forming a recombinant plasmid.

Insert the recombinant plasmid into a host bacterium (typically E. coli).

The bacterium reproduces rapidly — dividing every 20 minutes — producing millions of copies, each carrying the insulin gene.

Each bacterium reads the insulin gene and manufactures human insulin protein.

Insulin is extracted, purified, and supplied to people with Type 1 diabetes.

This process was first achieved in 1982, replacing the earlier method of extracting insulin from pig or cow pancreases. GM human insulin is purer, produced in much larger quantities, and avoids religious or ethical objections to animal-derived medicine. It is now the global standard.

What is cloning?

A clone is a genetically identical copy of an organism.

Natural cloning is more common than most students realise. Identical twins are natural clones of each other. Bacteria reproduce by binary fission — splitting into two genetically identical daughter cells. Many plants reproduce asexually via runners, bulbs, or tubers, generating offspring with identical DNA to the parent.

Artificial animal cloning became headline news with Dolly the sheep (1996), the first mammal cloned from an adult body cell, using a technique called somatic cell nuclear transfer (SCNT):

Take a body cell (a mammary gland cell) from the donor sheep (Finn Dorset ewe).

Remove its nucleus, which contains the donor's complete DNA.

Take an egg cell from a second sheep (Scottish Blackface ewe); remove its nucleus, leaving an empty egg cell.

Insert the donor nucleus into the empty egg cell, creating a reconstructed cell containing the donor's DNA.

Stimulate the reconstructed cell with an electric pulse to trigger cell division.

Implant the developing embryo into a surrogate mother sheep.

Dolly was born — genetically identical to the Finn Dorset donor.

Dolly lived to six years (a normal lifespan is around 12 years) and developed arthritis and lung disease earlier than expected, raising questions about whether shortened telomeres in the donor cell caused premature ageing in the clone.

What are the differences between reproductive and therapeutic cloning?

Both start with the same somatic cell nuclear transfer technique, but they diverge in purpose and outcome.

Reproductive cloning allows the cloned embryo to be implanted in a womb and develop into a full organism. Dolly is the definitive example. The goal is to produce a living, breathing clone. Reproductive cloning of humans is illegal in the UK and in most countries worldwide.

Therapeutic cloning creates a cloned embryo but harvests stem cells from it before it develops significantly. These embryonic stem cells carry the patient's own DNA, meaning tissues grown from them would not be rejected by the immune system. The embryo is not implanted and does not develop into a full organism. In the UK, therapeutic cloning research is permitted under strict regulation by the Human Fertilisation and Embryology Authority (HFEA) — though it remains ethically contentious because an embryo is destroyed in the process.

What are the ethical arguments for and against genetic engineering and cloning?

This is an area where scientific evidence and human values interact, and where thoughtful people disagree. At KS3 students are expected to be able to articulate arguments on both sides.

Arguments in favour:

Genetic engineering produces life-saving medicines — insulin, clotting factors, vaccines — at scale and purity impossible by traditional means.

GM crops could reduce hunger, improve nutrition (Golden Rice), and reduce the environmental burden of pesticide use.

Animal cloning could help preserve endangered species or propagate disease-resistant livestock.

Therapeutic cloning could yield personalised tissue for transplant with no rejection risk, potentially transforming treatment of conditions from Parkinson's disease to spinal injury.

Arguments against:

GM crops raise concerns about gene escape into wild plant populations, loss of biodiversity, and corporate control of the food supply; long-term ecological effects are not fully understood.

Many cloned animals have shown health abnormalities, premature ageing, or died early — raising serious animal welfare concerns.

Human reproductive cloning is widely considered unethical: it raises profound questions about identity, individuality, and the exploitation of cloned people.

Some hold that deliberately altering the genetic inheritance of a species crosses an ethical line that science should not cross — sometimes described as "playing God".

Frequently asked questions

What is a GMO and is GM food safe to eat?

A genetically modified organism (GMO) is any organism whose DNA has been deliberately altered using genetic engineering techniques. GM foods include herbicide-resistant soya, insect-resistant maize, and experimental crops such as Golden Rice. Major scientific bodies — including the World Health Organization, the Royal Society, and the European Academies Science Advisory Council — have concluded that currently authorised GM foods are as safe to eat as their conventional equivalents. In the UK, foods that contain or are produced from GMOs must be labelled. The ongoing public debate centres more on environmental and socio-economic concerns than on direct food safety.

What is the difference between genetic engineering and selective breeding?

Both aim to produce organisms with desirable traits, but they work very differently. Selective breeding (artificial selection) involves choosing organisms with wanted characteristics and breeding them together over many generations — a slow process confined to one species (or very close relatives that can interbreed naturally). Genetic engineering is far faster and can move genes between entirely unrelated species — from a bacterium to a plant, or from a human to a bacterium — which would be biologically impossible through breeding. Selective breeding can only recombine genes already present in the breeding population; genetic engineering can introduce wholly new genes that the recipient species has never possessed.

What is the significance of Dolly the sheep?

Dolly, born at the Roslin Institute in Edinburgh on 5 July 1996, was the first mammal cloned from an adult somatic (body) cell using somatic cell nuclear transfer. Before Dolly, the scientific consensus held that once a cell had differentiated into a specialised adult cell type, its DNA could not be "reprogrammed" to generate a whole new organism. Dolly proved that was wrong: the nucleus of a fully differentiated mammary cell could be reset to a totipotent state capable of directing the development of a complete animal. She lived for six and a half years — about half the normal lifespan for her breed — and developed arthritis and a progressive lung disease. These health issues sparked debate about whether cloned animals age prematurely because the donor cell's telomeres (protective caps on chromosomes) were already shortened from years of normal cell division.

Why is gene therapy different from genetic engineering of embryos?

Gene therapy targets the cells of a living patient — for example, inserting a working copy of a defective gene into lung cells to treat cystic fibrosis. The genetic change affects only the treated cells in that patient. The patient's germ cells are unaffected, so the change is not inherited by their children. Genetic engineering of embryos (germline editing) is fundamentally different: the change is made in the very first cell, so it will be present in every cell of the body and inherited by future generations. Germline editing in human embryos is currently banned or heavily restricted in most countries due to ethical concerns about heritable effects that cannot yet be controlled.

Explore genetic engineering, cloning, and all KS3 biology with Professor Darwin, your Socratic AI biology tutor — visit aitutors.me.