Scientists from a university in the USA have put us a step closer to engineering babies free of inherited disorders.

The team of scientists successfully used a ‘gene-editing’ tool in viable embryos. The tool is called CRISPR and makes it possible for scientists to remove and correct DNA with meticulous precision. The difference between this study and previous studies conducted in China is that the alteration had been made during fertilisation rather than after.

The feat comes amidst a debate on the ethics of genetic engineering. While disease free babies would most likely be welcomed with a positive consensus, the selection of other traits such as colour, build and intelligence remains controversial.

The study operated under rules relating to the progress of the embryos, as they were not supposed to develop beyond the point of a few days, after which they would become more than a handful of cells.

42 out of 58 embryos were resultantly free of a mutation causing heart disease which was carried by the sperm used to create them, equating to a 72 per cent success rate. This is an improvement from the 50 per cent disease free rate of naturally born embryos, in which one person in a couple carries the coding error.

Co-author of the study, Paula Amato of the Oregon Health and Science University, explained that with more progress the method could “potentially be used to prevent transmission of genetic disease to future generations”.

Since the alteration is heritable, babies born with the edited DNA will go on to have children and grandchildren free of the genetic disease. The method will have to reach success rates as close to 100 per cent as possible before it can be used on embryos intended to develop into babies.

On the topic of the controversy around DNA editing, Darren Griffin of The University of Kent said: “Equally, the debate on how morally acceptable it is not to act when we have the technology to prevent these life-threatening diseases must also come into play.”