Currently, testing for genetic disorders can only identify a very small percentage of the 15,000 known ones. However, a new test is on the horizon that has the potential to screen for nearly every kind of genetic disease.
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The idea of a some sort of universal test that would be able to spot a genetic mutation or predisposition to a genetic disorder would be something of a major technological advance. It would eliminate the worry faced by many parents who conceive by IVF and fear that they may pass a particular gene defect to their offspring. However, it would also anger many critics who have deeply held ethical objections to the creation of so-called 'designer babies.'
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A universal test could be on the market as soon as early 2009. It's being developed in the UK by the Bridge Centre, a specialist fertility clinic based in London. The Times newspaper has been reporting that it could come on the market at a cost of approximately £1,500.
This new kind of genetic testing would involve the removal of a single cell from an embryo created by IVF. The cell would then be tested by a process known as karyomapping. Here embryonic DNA is compared with DNA that has already been obtained from parents and a close relative. In this way a picture is able to be constructed of the embryo's chromosomes to see what has been inherited from parents and grandparents. The results could come through within a matter of weeks.
This is a significant advance on current pre-implantation genetic diagnosis which can take up to a year. Though a few hundred conditions, such as Huntington's disease and cystic fibrosis can be tested, the scientists first have to find the specific genetic mutation and then develop a test for it. That's why it takes so long.
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How Karryomapping Works
During gametogenesis a father's sperm and a mother's eggs are created by cell division and include chunks of DNA from their parents (the embryo's grandparents).
Scientists then draw up a chart of where the chromosomes came from by comparing DNA of embryo, parents and a close relative. They will be able to examine more than 300,000 DNA markers so see which grandparent provided a block of DNA.
It is not necessary to look for specific genetic mutations. For example if a grandparent had cystic fibrosis, the gene that causes it lies on chromosome 7. If the embryo has inherited this chunk of DNA, it will be easily spotted. The same is true of many other conditions.
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The new technology raises several important issues, and one of those is privacy. For example, as well as informing parents about the risk of children inheriting disorders such as cystic fibrosis it could also let them know about a child's future prospects of having a predisposition to life threatening diseases such as Alzheimer's or heart problems. The privacy of the child as been invaded because he or she could not possibly give consent to such private information being made public.
The new test would also be able to identify those embryos at risk of dying before the end of pregnancy. This knowledge could be used to increase to chances of a successful birth for prospective parents.
The test could not be used for sex selection for social reasons. This is banned in Britain, though screening is permitted for inherited conditions that only affect boys.