ack in February 2015, Parliament
voted to amend the 2008 Human
Fertilisation and Embryology Act to
allow ‘three-parent IVF’ for families that
carry mitochondrial diseases. These diseases
are coded in the genes and are passed from
mum to child via the mitochondria, the
‘batteries’ of the cell.
Mitochondria are tiny disc-shaped
organelles (minuscule organs) carried within
cells. The primary function of mitochondria
is to produce ATP, the biological currency
of energy. The number of mitochondria
varies widely between cell types: red blood
cells do not contain any, but liver cells can
hold up to 2,000 each.
Human egg cells contain mitochondria the
way most cells do, but sperm cells only have
them in their tails. During fertilisation, the
head of the sperm, which contains its genes,
is inserted into the egg. The tail of the sperm
- and therefore its mitochondria – is left
behind. This is why all of us only inherit our
mitochrondrial DNA from our mothers.
Malfunctioning mitochondria can
produce a wide variety of illnesses for
which we have no cure. They regularly
strike the organs that have the greatest
energetic demands, including the kidneys,
heart, liver, brain, muscles and central
nervous system. Mitochondrial conditions
are often fatal in infancy, but can
frequently strike in adolescence or
adulthood. It is estimated that one in 200
children in the UK carries some form of
genetic mutation that could lead to
mitochondrial disease at some point in
life. Every year, one in 6,500 babies is
born with a mitochondrial condition so
severe that they will not reach adulthood- or even their first birthday.
“Mitochondrial diseases are horrible and
cruel – especially because as a parent there is
nothing you can do,” says Liz Curtis, whose
daughter Lily died at eight months old from
Leigh Syndrome. While Lily died when she
young, others live for five or ten years,
slowly deteriorating. “To watch a child lose
the ability to walk, talk, eat and eventually
smile is crushing,” says Curtis. She set up the
Lily Foundation in her daughter’s honour to
support the families of children coping with
mitochondrial conditions and to fund
research into potential cures – because none
were available to prevent Lily’s death.
SILENT KILLER
Currently in the UK, more than 150
children a year are born who will suffer
severe mitochondrial disease – often
unbeknownst to them or their
families. And new research hints thatB
THE UK COULD FINALLY WITNESS THE BIRTH OF A
CHILD WITH DNA FROM THREE PARENTS, AS ZOE
CORMIER REPORTS
DAWN OF THE
GM BABIES
DNA DECIPHERED
Almost all human DNA – 99.9 per cent
of it - is contained in the nucleus at
the centre of a cell. In the nucleus,
information is stored and instructions
are dispatched.
The three billion ‘letters’ of the human
genome – which come in four chemical
building blocks, called cytosine, adenine,
thymine and guanine, are linked in long
strands of DNA, called chromosomes.
Each of us has 46 chromosomes,
bound in 23 X-shaped pairs. The human
genome consists of around 20,000
genes. Each gene is a stretch of DNA
coding for a particular protein.
Other than the nucleus, the mitochondria
are the only other organelles of the cell that
contain DNA in their own genome. The
mitochondrial genome – first discovered
in the 1960s – is tiny, with just 37 genes.
Though the mitochondrial genome
accounts for just 0.1 per cent of the human
genome, it holds the distinction of being
the first portion of it be fully mapped:
geneticists managed to describe its
contents in the 1980s, partly
due to the fact that it
is so small.Vol. 8 Issue 3Vol. 8 Issue 3 2929