'Aneuploidies are seen in at least 5% of all pregnancies and are therefore a big cause of human illness, death and miscarriage. This technology will provide a crucial genetic tool in understanding this complex human syndrome.'

Their work aids understanding of the health problems associated with a class of disorders known as "aneuploidies," in which individuals have the wrong number of chromosomes.

Dr. Victor Tybulewicz of the National Institute for Medical Research and Professor Elizabeth Fisher of the Institute of Neurology, University College London, led the research.

Heart, Brain Abnormalities

Down's syndrome, a genetic condition that occurs in around 1 in every 750 births, is caused by the presence of three copies of chromosome 21 instead of the normal two. As yet, it is not clear what causes this extra chromosome to be present.

The researchers placed almost the entire human chromosome 21 into mouse embryonic stem cells. They then manipulated these cells to generate a mouse that carries the human chromosome to model Down syndrome.

The new mouse strain exhibits problems similar to those that can occur in people with Down's syndrome: deficiencies in memory and brain function, and abnormal formation of the heart.

Crucial Genetic Tool

"Aneuploidies are seen in at least 5% of all pregnancies and are therefore a big cause of human illness, death and miscarriage," said Dr. Tybulewicz.

"This technology will provide a crucial genetic tool in understanding this complex human syndrome," he added.

"People with Down syndrome have particular susceptibilities for some diseases like leukemias and autoimmune disorders," noted Professor Fisher. "We believe this new technology will help us work out why this is, and what to do about it."

Colleagues at the new Institute of Cell and Molecular Science of Queen Mary's School of Medicine in London, the University of Newcastle, Kings College London and the MRC Prion Unit collaborated on the research, which was funded by the MRC and the Wellcome Trust.