Scientists recreate Down's syndrome in mice

The Medical Research Council hope it will help research into that and other chromosomal conditions.

The mice, who carry 92 per cent of a copy of human chromosome 21, display the characteristic symptoms of Down's syndrome; problems with memory, brain function and the formation of the heart.

The research, published in the magazine Science, is a significant technical development in the study of the disease and other diseases that stem from chromosomal abnormality. Down's syndrome affects almost one in 750 babies.

Victor Tybulewicz at the National Institute for Medical Research, and Professor Elizabeth Fisher from the Institute if Neurology at University College London, led the research. Previously it had only been possible to place fragments of chromosomes into mouse cells, and no mouse had displayed a heart disorder similar to Down's.

Professor Elizabeth Fisher of the Institute Neurology, one of the lead scientists on the research, told the BBC: "This is a technical step forward in stem cell technology. "People with Down's syndrome have particular susceptibilities for some diseases such as leukaemias and auto-immune disorders, which affect the rest of us as well. We believe this new technology will help us work out why this is, and what to do about it."

She added: "We also hope it will help unravel the picture of individual genes responsible for complex conditions, such as diabetes, and to create artificial chromosomes for gene therapy."

Most people have 23 pairs of genes but a person with Down's has three copies of chromosome 21, instead of the normal two.

While it is not to be considered as a cure for Down's syndrome, scientists hope the strain of mice, named Tcl, will improve the understanding of other human chromosome disorders. Collectively, they occur in at least 5 per cent of all pregnancies and are a significant cause of illness, death and miscarriage.

The diseases, known as aneuploidies, include Edward's syndrome, where there are three copies of chromosome 18 and Patau's syndrome, where chromosome 13 is triplicated.