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DNA swap technique may block inherited diseases.

DEVASTATING inherited diseases could be prevented using a pioneering fertility technique to swap DNA between eggs, scientists believe. The British breakthrough opens up the possibility of avoiding mitochondrial disorders which can lead to early childhood death.

The diseases are caused by defective DNA in mitochondria - bean-shaped bodies in cells that act like batteries to generate energy. About one in 6,500 children in the UK is severely affected by the disorders, which can cause muscle weakness, blindness, heart and liver failure, diabetes and learning disabilities.

Mitochondria DNA is separate from that of the cell nucleus and contains far fewer genes. It is only passed from mothers to their children.

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There are no treatments available which can cure mitochondrial diseases. Mothers with a family history of the disorders normally face the agonising choice of risking having an affected child or no child at all. The new technique developed at the University of Newcastle raises hopes of ensuring a baby does not inherit malfunctioning mitochondrial DNA. It involves transferring nuclear DNA inherited from a child's parents to a donor egg carrying its own, properly functioning, mitochondria.

"What we've done is like changing the battery on a laptop," said Professor Doug Turnbull, one of the study leaders.

"The energy supply now works properly, but none of the information on the hard drive has been changed.

"A child born using this method would have correctly functioning mitochondria, but in every other respect would get all their genetic information from their father and mother."

Mitochondrial DNA only affects energy production, not all the characteristics that make a person a recognisable individual.

The mitochondria contain around 13 genes compared with an estimated 23,000 in the cell nucleus.

Members of the Newcastle team used a DNA-transfer technique similar to that employed in cloning. A newly fertilised egg normally contains two "pronuclei" containing genetic material from the egg and sperm as well as mitochondrial DNA. Soon after fertilisation, the pronuclei fuse to form a single nucleus.

The scientists extracted the pronuclei from fertilised eggs in the laboratory, leaving behind the mitochondria. They then implanted the pronuclei into fertilised donor eggs whose own pronuclei had been removed. The eggs were left with the transferred pronuclei plus working mitochondria from the women who donated them.
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Publication:Western Mail (Cardiff, Wales)
Date:Apr 15, 2010
Words:377
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