Embryo test to screen for genetic disease

A MAJOR new embryo screening advance could allow many more couples to avoid passing inherited disorders on to their children.

The British breakthrough is similar to the genetic fingerprinting technique used in police inquiries.

Five couples who have undergone the test are now expecting healthy babies after In-Vitro Fertilisation (IVF).

Experts hope hundreds more couples will soon be helped by the technique each year, and in future it may be used to screen out thousands of genetic diseases.

But ethical campaigners fear doctors have taken another step towards “designer babies” created according to parents’ specifications.

The standard screening test, known as pre-implantation genetic diagnosis (PGD), involves identifying specific mutations in genes.

But this process can take up to a year and does not work for every disorder.

About 1,000 mutations are thought to cause the inherited disease cystic fibrosis, but only one, the most common, can be identified by PGD. The new test, called pre-implantation genetic haplotyping (PGH), instead looks for chromosomal “markers” in DNA. Finding these abnormal signatures means defective chromosomes can be spotted without having to zero in on specific mutations.

It can take as little as two months to carry out and has the potential to detect many more disorders than traditional PGD.

Professor Peter Braude, who developed the technique at Guy’s Hospital in London, said: “We don’t have to know the precise details of a mutation, just whereabouts it is in the genome.

“It is more accurate and reliable than PGD and could be available for a whole range of disorders.”

For the test, blood samples are taken from a couple, and any affected children or relatives. DNA from these samples is tested and compared.

Using a technique to create many more copies of chromosomes in the lab, scientists look for markers that show if an embryo carries the problem chromosome or a disease-free version.

Only healthy ones are implanted into the mother’s womb.