A Russian scientist has revealed he wants to use controversial DNA editing to stop deaf couples having deaf children.
Denis Rebrikov, a biologist, said he knows five couples with inherited deafness who are worried about their children being born with the same condition.
The deafness is caused by a missing part of DNA which stops someone's hearing ever developing.
Mr Rebrikov believes he can use pioneering CRISPR gene-editing science to repair this DNA error and stop the couples passing on the disability to their children, the New Scientist reports.
But he has come up against criticism from scientists in the field who warn the untested surgery is 'too risky'.
They have drawn comparisons to a disgraced Chinese scientist who secretly edited the DNA of babies to try and protect them from HIV.
Denis Rebrikov, who works out of a fertility clinic in Moscow, said he believes he has found the only way to stop hereditary deafness in five families in western Siberia
'Rebrikov is definitely determined to do some germline gene editing, and I think we should take him very seriously,' the Australian National University's Dr Gaetan Burgio told the New Scientist.
'But it’s too early, it’s too risky.'
CRISPR works by essentially cutting and pasting sections of DNA to change how someone's genetics affect their body.
For someone with a genetic disorder, for example, a corrected gene could be created in a lab and then surgically implanted into their body to try and cure an illness.
The science is still in its infancy in human medicine and there are huge concerns about the medical and ethical implications of using it.
People fear fiddling with patients' DNA could have serious, long-term and even life-threatening effects, and that it could be used to create 'designer babies'.
CRISPR works by cutting DNA in a precise place, allowing small portions of a gene to be removed and replaced with a different one created in a lab
But on the flipside, it has shown promise for treating people with conditions which are currently difficult or impossible to cure, such as cancer, genetic illnesses like Tay-Sachs disease, and inherited disabilities like the couples' deafness.
Mr Rebrikov hopes to carry out his work at his lab in the Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology in Moscow.
He said: 'It is clear and understandable to ordinary people. Each new baby for this pair would be deaf without gene mutation editing.'
The CRISPR gene editing technique is being used an increasing amount in health research because it can change the building blocks of the body.
At a basic level, CRISPR works as a DNA cutting-and-pasting operation.
Technically called CRISPR-Cas9, the process involves sending new strands of DNA and enzymes into organisms to edit their genes.
In humans, genes act as blueprints for many processes and characteristics in the body – they dictate everything from the colour of your eyes and hair to whether or not you have cancer.
The components of CRISPR-Cas9 – the DNA sequence and the enzymes needed to implant it – are often sent into the body on the back of a harmless virus so scientists can control where they go.
Cas9 enzymes can then cut strands of DNA, effectively turning off a gene, or remove sections of DNA to be replaced with the CRISPRs, which are new sections sent in to change the gene and have an effect they have been pre-programmed to produce.
But the process is controversial because it could be used to change babies in the womb – initially to treat diseases – but could lead to a rise in 'designer babies' as doctors offer ways to change embryos' DNA.