Rare diseases can be prevented by DNA egg swap.
scientists have mastered a controversial technique using cloning
technology to prevent some incurable inherited diseases by swapping DNA
fertilized human eggs
Lead researcher Doug Turnbull of Newcastle
University said on Wednesday he hoped the first babies free from
so-called mitochondrial diseases would be born within three years.
But applying the technique in the clinic,
to help women at risk of passing on the disorders, will require a change
in British law that currently bans reproduction from such manipulated
embryos, which would end up having three biological parents.
Around one in 6,500 children are born with
serious diseases caused by malfunctioning mitochondrial DNA, leading to a
range of conditions that can include fatal heart problems, liver
failure, brain disorders, blindness and muscular weakness.
The Newcastle team's technique effectively
replaces mitochondria, which act as tiny energy-generating batteries
inside cells, so a baby doesn't inherit faults from its mother.
Mitochondria are only passed down the maternal line.
"What we've done is like changing the
battery on a laptop. The energy supply now works properly, but none of
the information on the hard drive has been changed," Turnbull said.
"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."
The researchers use a variation of the same
technique used to make Dolly the cloned sheep in 1996.
Within a day of uniting egg and sperm using
in vitro fertilization, nuclear DNA is removed from the embryo and
implanted into a donor egg, whose own nucleus has been removed and
Two or three parents?
The resulting embryo inherits nuclear DNA,
or genes, from both its parents but mitochondrial DNA from a second
"mother" who donated the healthy egg. In humans, about 37 genes are
found in the mitochondria -- the rest of the more than 20,000 known
genes are in the DNA found in the nucleus.
critics like Josephine Quintavalle of campaign group Comment on
Reproductive Ethics that makes it "a step too far in meddling with the
building blocks of human life."
matter how small the contribution from the egg of the donor woman, the
fact remains that an attempt is being made to create a three-parent
child," she said.
Murdoch of the Newcastle Fertility Center, whose patients donated eggs
used in the studies, told reporters such criticisms ignored the fact
that all the characteristics of the baby would come from its two real
Researchers in Newcastle
first disclosed two years ago they had created a handful of embryos with
swapped DNA, but it is only now that the process has been shown to
produce viable embryos.
the journal Nature, the team said 80 embryos were created and developed
in the laboratory for six to eight days to reach the blastocyst stage,
comprising a ball of around 100 cells. They were then destroyed, in line
with current rules.
Would you do this to prevent your child from having a rare disease?