article: Many researchers thought ministers would sit on this controversial issue. Instead, the chief medical officer, Professor Dame Sally Davies, has announced that draft regulations will be published within months. She predicts that couples affected by mitochondrial disease could benefit from the treatment within two years, enabling them to have healthy children. So why is this such a significant moment? Firstly the UK will become the first country to allow the technique, aimed at preventing a range of potentially deadly genetic disorders. This will underline Britain's pioneering role in genetics and IVF stretching back to both the discovery of the structure of DNA in 1953 and the birth of Louise Brown, the world's first test tube baby, in 1978. Secondly, the technique itself will result in babies with DNA from three people - two women and a man - and this genetic alteration will be passed down the generations. Once babies have been born using this technique, there will be no going back. A permanent and novel genetic change to members of the human race will have been made. That might sound pretty worrying, and talk of three people's DNA mixed together seems a bit ghoulish at first glance. So is this science overstepping the mark? A public consultation conducted by the fertility regulator, the HFEA, found there was broad support for the technique, once the details had been explained. So let's look briefly at the science. Mitochondria are the energy factories of cells. They contain a tiny bit of DNA and just 37 genes, sitting outside the nucleus which has more than 20,000 genes - including all the crucial genetic material from both parents. Mitochondrial disorders are always passed down the maternal line in the egg, so the technique being pioneered by Prof Doug Turnbull and his team at Newcastle University involves using healthy donor eggs. Put briefly, conventional IVF is performed and then, after fertilisation, the pro-nuclei of the father and mother - you can see them clearly as the two round balls inside the glass tube in the picture above - are sucked out of the developing embryo. This leaves behind the faulty mitochondria. The parents' genetic material is then injected into a healthy donor egg which has had its pro-nuclei removed but still has healthy mitochondria. The scientists believe the resulting embryo should develop normally. It means all the crucial parental genes will be retained, plus a tiny amount of DNA from the female donor. So how much DNA from the second woman is there? There is 1.05 metres of DNA in the nucleus and 0.0054 mm of DNA in our mitochondria. Let's put that another way. If you imagine the DNA in your nucleus - remember this is all the important stuff which makes us what we are - and stretched it from Trafalgar Square to Prof Turnbull's laboratory in Newcastle, you'd have a double helix of 282 miles. Now if you laid all the DNA from the mitochondria alongside it, it would stretch from Trafalgar Square, barely round the corner to the National Portrait Gallery - just
summary: The decision of the government to support a ground-breaking technique for preventing serious genetic disease is a bold step for science and society.