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Professor Ian Craft
"The public do want this"
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banner Thursday, 5 July, 2001, 07:45 GMT 08:45 UK
Choosing baby sex made easier
Modern techniques allow parents to chose the sex of their baby
A method of spotting sperm which will produce a female embryo could allow parents to choose the sex of their child with more certainty than ever.

The breakthrough has raised concerns that the technology could be abused by people wanting to determine their child's sex for purely social reasons.

US researchers claim their method is accurate on nine out of ten occasions, and say that their technique could help couples to avoid passing on genetic illnesses which usually affect only boys.

It substantially increases the chance of a couple having a child of a particular gender

Dr Harvey Stern
It is the contents of the sperm which decide whether a baby will be male or female.

While a normal cell in a man will carry both a female, or X, sex chromosome, and the one which produces male characteristics, called the Y chromosome, a single sperm carries only one, which can be either X or Y.

Because a woman's cells carry two X chromosomes, the egg will always have the X chromosome.

When a sperm fertilises the egg, if it carries the X chromosome, it will produce an X female embryo, while if carries the Y, a boy will be created instead.

The theory behind sperm separation is finding a way of beating these 50:50 odds by sorting X from Y.

Heavy X

The key difference between the two is that the X chromosome is substantially larger than the Y chromosome - carrying 2.8% more DNA.

The MicroSort technique, developed at the Genetics and IVF Institute in Fairfax, Virginia, exploits this difference.

Professor Ian Craft
Professor Ian Craft admitted the technology could be open to abuse
Dr Harvey Stern, presenting the team¿s work at the European Society of Human Reproduction and Embryology congress in Lausanne on Wednesday, said the device was currently undergoing a clinical trial, but experiments so far had been highly successful.

He said: "We were able to be unambiguous in assigning gender in 90% of the 284 embryos.

"Of these, 92% were female and 8% were male. It substantially increases the chance of a couple having a child of a particular gender."

Researchers would be keen to stress that the device should not simply be seen as a frivolous "lifestyle" technique for those who would prefer a female child, perhaps because they had existing male children.

Double chance

Many devastating genetic disorders, such as haemophilia and muscular dystrophy are caused by defects on the X chromosome.

Most of these are "recessive", which effectively means they can be overruled if there is another X chromosome present with the correct genetic information on it.

If one parent is carrying the defective X chromosome, then there is a 50% that a mother, and a 100% chance that a father will pass it on to the child.

If the child is female, it will have two X chromosomes - and unless both parents are carrying the defect and have passed it on, which is highly unlikely, the "good" chromosome will cancel out the defect.

However, if the child is male, carrying both the X and Y chromosomes, there is no second X to overrule the defective one, and receiving a defective X means the disease will definitely emerge.

Possible abuse

Ultimately we have to wonder whether will you ever have sex selection kits available at your chemist

Professor Ian Craft
Professor Ian Craft, head of the London Fertility Clinic, said similar work was being carried out in the UK- but not with such impressive results.

He admitted that there was a concern that the process could be abused for social reasons, and said the law would have to be changed if new controls were to be introduced.

"We have to face facts, the public do require this sometimes, whether it is for inheritance reasons, or balancing their families. They will go to any lengths to have a child.

"Ultimately we have to wonder whether will you ever have sex selection kits available at your chemist, whereby you add something to your semen sample and get an X chromosome or a Y."

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07 Dec 00 | Health
Sex 'boosts IVF chances'
22 Jun 01 | Health
Heart link to problem pregnancies
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