Kiyoshi Takahase Segundo / Getty Images Allowing scientists to modify human embryos is vital to fundamental research, and could give new hope to would-be parents undergoing IVF, according to researchers in the field.Dr Kathy Niakan, an embryologist at the Francis Crick Institute, has applied to the Human Fertilisation and Embryology Authority (HFEA) for permission to use genetic modification techniques on human embryos. If it is granted, scientists say they will be able to see the effects of removing or adding different genes on the development of the embryo, and whether those genes are involved in – for instance – the termination of pregnancies. They will also be able to remove genes that are known to be involved in certain diseases. The experiments will use a genetic technique called CRISPR. Using a system borrowed from bacterial genes, it allows scientists to target short DNA sequences in the genome, cut them out, and replace them. Studies of this kind have been done in mice, but never before in humans by UK scientists.The HFEA has yet to make a decision, although a Crick spokesperson told BuzzFeed News that scientists are hopeful that the licence will be granted, given that UK law already allows other kinds of experiments on human embryos."It's a huge game-changer," Professor Darren Griffin, a geneticist at the University of Kent, told BuzzFeed News. He said CRISPR is already revolutionising research in genetics: "You can, with a great deal of confidence, target an individual gene, and perform much more controlled and targeted experiments."Niakan's research area is the growth of the early embryo, and she hopes it will shed light on why many pregnancies fail in the first few weeks. "The knowledge we acquire will be very important for understanding how a healthy human embryo develops, and this will inform our understanding of the causes of miscarriage," she told The Guardian. Critics have expressed concern that allowing scientists to modify human embryos could pave the way for genetically modified babies. However, Niakan and others say this is not a plausible risk. "It is not a slippery slope [towards designer babies] because the UK has very tight regulation in this area," Niakan said. The embryos used in research are surpluses from IVF and would otherwise be disposed of, and under UK law they must be destroyed by the time they are 14 days old.There are also concerns over safety, but so far the evidence suggests that the technique is safe. "If for instance by introducing this you could damage the DNA in some other way, that is a question that we need to ask," said Griffin. "At the moment it's looking very promising."The techniques "will allow a better understanding of how early human embryos develop in the laboratory, what makes them succeed or fail after IVF, and what is needed to develop clinically useful stem cells", said Peter Braude, an emeritus professor of gynaecology at King's College London, in a statement released to the Science Media Centre. "This is about better understanding nature, not changing embryos for implantation." Griffin warned, however, that it is impossible to say how long it would be before would-be parents started seeing effects. "It depends both on the progress of the science and the reaction of the public and the regulatory bodies," he said, "but the timescale will be years rather than months."At the moment there is no call for the use of genetic modification techniques on embryos which will be implanted and become children. However, that "will inevitably be part of the debate in future", Griffin said. The technique has such great potential, he said, "If you don't do it, are you then responsible for not letting happen the benefits that it might have?"