Imagine you had a word document filled with letters that were the code for everything about you – the way you look, how your brain works, the diseases you might get.

This is your DNA, the recipe for you, and scientists have found a way to edit it, just like in Word, with the precision of a double click. This technique is called CRISPR and it’s being proclaimed as the biggest advance in medical research in decades. CRISPR is the latest news in a research field called gene therapy.

Gene therapy is the use of genes as medicine and works in a number of ways. Originally gene therapy was developed for diseases that are caused by single mutations in a gene for example cystic fibrosis or haemophilia.

Scientists try to replace the mutated gene with the correct gene and therefore stop the disease.

One of the biggest challenges with this approach is that there are a lot of cells in your body – each with that bit of mutated gene so getting the corrected gene to the right place in each cell is very difficult. It is a bit like realising you have made a mistake on page 542 of a 10,000 page document and having to send that single page to 30 trillion locations across the world all at once!

Once it arrives you then have to hope it gets put in the right place.

Another gene therapy approach is to use genes as medicine. Scientists design pieces of DNA, called therapeutic genes that are introduced into the body to fight disease. Some scientists here in Oxford are doing just this. One group, led by Professor Len Seymour, is working on a gene therapy for cancer.

They have taken a simple cold virus, removed all the genes that enable the virus to give you a cold and replaced them with genes that kill cancer.

They manipulate the surface of the virus so that it becomes a homing pigeon for cancer cells, taking the therapeutic gene directly to the cancer. This means that the healthy cells are less effected and the patient avoids nasty chemo side effects.

As you would expect with anything completely new there have been challenges for gene therapy scientists. This is where CRISPR may make a world of difference.

CRISPR is an enzyme that acts like a very accurate pair of scissors especially for DNA. You tell it where to snip the DNA and it will do it with unprecedented accuracy. It is also fast and efficient so many of the challenges with getting those therapeutic genes into lots of cells in exactly the right place might be a thing of the past.

CRISPR looks promising and we need to start talking about what it means to us as a society.

The ability to accurately and effectively treat disease through our genes is an exciting medical advance but only with good communication and debate will we be able to ensure that it is used in the ways we want.