Scientists may have found a new way of introducing genetic changes which are passed from parent to child.

But there are still many obstacles to be crossed before a way can be found to eradicate a genetic illness completely from both the patient and subsequent generations of their family.

Researchers now know much more about the function of thousands of genes found in every human cell.

In some people, mutations in certain genes may cause a malfunction in the cell, and the body at large, leading to disease.

The idea behind conventional gene therapy is to find a way to reduce the effects of the errant gene by inserting new versions that work properly.

Handed down

In humans, the "germline" of genetic information passed from parents to child can be found in the sperm and the egg.

In order to manipulate the genetic fate of the child - and generations to come - either these germ cells would have to be altered, or the child itself modified in the very first days of its existence in embryo form.

In the latest study, scientists have found a novel method of doing this in mice.

They are using a technique called RNA interference, which can switch off a gene or reduce its activity, stopping the cell from behaving in a certain way.

They introduced the change into stem cells, extracted from early mouse embryos, then injected these genetically modified cells into the target mouse embryos.

They found that not only were the changes taken up in these animals, but also in many of the first generation of their offspring.

Long way off

Despite the effectiveness of the therapy in these animals, treatments for humans are still on the distant horizon, and the new method may not prove suitable.

Mice have embryonic stem cells which can play a role in the creation of every tissue in the body - humans do not.

Dr Maggie Dallman, from Imperial College London, UK, said the research, published in the journal Nature Structural Biology, was "very exciting experimentally".

However, she said: "If you are talking about changing the human germline, then this is not necessarily the method I would choose to do it."

However, in the meantime, the technique could provide another option for scientists to examine the consequences of tampering with the genes of experimental animals, perhaps speeding up the process of producing human therapies.