Scientists have transplanted a nearly entire human chromosome in mice in a medical and technical breakthrough that could reveal new insights into Down’s syndrome and other disorders.

The genetically engineered mice carry a copy of the human chromosome 21. It is the smallest of the 23 pairs of human chromosomes with about 225 genes.

Children suffering from Down’s syndrome, which is one of the most common genetic disorders, inherit three copies of the chromosome instead of two.

The achievement caps 13 years of research by scientists at the National Institute for Medical Health in London and the Institute of Neurology.

“We are very optimistic that we will be able to get insights into what goes wrong with people with Down’s,” said Dr Victor Tybulewicz, who headed the research team.

Down’s syndrome, which affects about one in every 800 live births, causes delays in mental and physical development. People with the condition may also have heart defects, hearing problems and have a higher risk of suffering from leukemia and early-onset Alzheimer’s disease.

“These disorders that people with Down’s are more prone to get are ones that also affect all humans. It is entirely possible that if we gain insights into what is going wrong in the Down’s syndrome people we will also gain insights into what goes wrong during those disorders amongst the rest of us,” he added.

Dr Elizabeth Fisher, of the Institute of Neurology, said the technology will help scientists tease out the genes that cause the different aspects of Down’s syndrome and susceptibility to other diseases.

“We believe this new technology will help us work out why this is, and what to do about it,” she said.

By Patricia Reaney

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