18.2 Genetic Modification

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1. What Is Genetic Modification?

Every living organism has DNA — a long molecule found inside cells that carries all the instructions for how that organism grows, functions, and looks. These instructions are organised into sections called genes. Each gene is a specific sequence of DNA that controls one particular characteristic or process — for example, eye colour, height, or the ability to produce a certain substance.

Genetic modification (GM) means deliberately changing the genetic material of an organism. Scientists can do this in three main ways:

• Removing a gene — cutting out a gene so that the organism no longer has the instructions for a particular trait
• Changing a gene — altering the sequence of a gene so that it works differently
• Inserting a gene — taking a gene from one organism and placing it into the DNA of a different organism

The organism that receives a new gene from another species is called a genetically modified organism (GMO). The inserted gene will then be read and used by the new host organism, allowing it to produce something it could never produce before.

2. Insulin Production Using Genetically Modified Bacteria

Background: What is insulin and why do we need it?

Insulin is a chemical substance (a protein hormone) that your body uses to control the level of sugar (glucose) in your blood. When you eat, your blood glucose rises. Insulin tells your body's cells to absorb that glucose, bringing the blood sugar level back down to normal.

People who have Type 1 diabetes cannot produce their own insulin. This is because their immune system has destroyed the cells in the pancreas (an organ in the body) that make insulin. Without insulin, blood sugar rises dangerously high, which can cause serious health problems and even death. These people must take insulin regularly to survive.

The solution: Genetically modified bacteria

Scientists solved this problem by using genetic modification to make bacteria produce human insulin. Here is how it works:

Step 1 — Identify the gene: Scientists identified the specific human gene that carries the instructions for making insulin. This gene is found in the DNA of human pancreatic cells.

Step 2 — Extract the gene: Using special biological "scissors" called restriction enzymes, scientists cut the insulin gene out of the human DNA.

Step 3 — Insert the gene into bacterial DNA: Bacteria contain small circular loops of DNA called plasmids (separate from their main DNA). Scientists cut open a bacterial plasmid using restriction enzymes and inserted the human insulin gene into it. The plasmid is then put back into the bacterium.

Step 4 — The bacterium reads the new gene: The bacterium now contains the human insulin gene. Because all living cells use the same basic genetic code, the bacterium can read this human gene and follow its instructions — producing human insulin.

Step 5 — Commercial production: The bacteria are grown in huge tanks called fermenters. Because bacteria reproduce very rapidly (doubling in number every 20 minutes or so), enormous quantities of insulin can be produced in a short time. The insulin is then extracted, purified, and packaged for use by diabetic patients.