HUMAN embryos with three parents have been created by British scientists.
In a world first procedure, IVF embryos each containing DNA from one man and two women were produced as part of a medical research project on serious inheritable diseases by a team at Newcastle University.
The technique is being developed in the hope of eventually helping women with diseases of the mitochondria - power packs inside cells that convert food to energy - avoid passing on their genetic defects to their children. About half the children born with mitochondrial disease in Australia die before the age of two.
But critics argue the research is a worrying step towards creating genetically manipulated, or "designer" babies.
Greg Pike, director of the Southern Cross Bioethics Institute in Adelaide, said the ethical implications would be profound if the new technique was ever used, because it was not known how the children would react.
"The possibility of having three biological parents is an entirely new scenario which constitutes experimentation with human life," Dr Pike said.
The creation of embryos with more than two genetic parents is banned in Australia but the British experiments, which were reported in London's Daily Telegraph, were approved there.
Mitochondria have their own DNA, separate to that in the cell's nucleus. It is only passed down from mother to child via her egg.
Defects in mitochondrial DNA can lead to about 50 diseases, including blindness, mental retardation, epilepsy, muscle weakness and diabetes.
About one in 5000 births are affected by the conditions, which develop at different ages and often lead to premature death.
The Newcastle team hopes the new "mitochondria transplant" technique, which they tested using 10 IVF embryos that were only allowed to develop for six days, could eventually eradicate the diseases.
The idea is that couples could create an IVF embryo with their own sperm and egg. Then their nuclear DNA would be removed and implanted in an egg donated by a woman who does not have mitochondrial disease.
Her nuclear DNA would be removed from the egg so the child would only have nuclear DNA that influences appearance and characteristics from the real parents.
David Thorburn, of Murdoch Children's Research Institute in Melbourne, said it was difficult to comment on the British experiments because they were not yet published in a scientific journal.
But he thought the research was worth pursuing, because there were few options for families with mitochondrial disease who wanted to ensure they had unaffected children.
"I would like to see more data about the safety issues," Associate Professor Thorburn said.
The Melbourne institute has diagnosed about 400 Australian children with mitochondrial disease in the past 15 years.
The law would have to be changed in Britain before the technique could be used to produce children.
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