Friday 16 December 2016

Three-Parent Babies All You Need To Know

Three-parent Babies

A controversial new fertility treatment that leads to babies with three genetic parents has been approved by regulators in the UK .

The decision by the Human Fertilisation and Embryology Authority (HFEA) paves the way for the first mitochondrial replacement therapy (MRT) procedures to go ahead next spring.

Scientists at the University of Newcastle, which has pioneered the treatments, say they already have women lined up for the therapy.

But what is MRT and how does it work? We answer your questions:

What are mitochondria?

Mitochondria are tiny rod-like structures in cells which act as power houses, generating the energy that allows our bodies to function. Unusually, they have their own DNA, distinct from the genetic material within the cell nucleus.

Three-parent Babies

Mitochondrial DNA (mtDNA) makes up about 0.1% of a cell's total DNA and does not affect individual characteristics such as appearance and personality.

What causes mitochondrial disease?

Harmful mutations in mitochondrial DNA can prevent the mitochondria working properly, resulting in a number of diseases, some of which can be serious and life-threatening. They may affect major organs and cause conditions ranging from poor vision to diabetes and muscle wasting.

How are mitochondrial diseases passed on?

Children may inherit mitochondrial DNA defects from their mothers, but not their fathers. People with faulty mtDNA can develop symptoms or be carriers of the condition without experiencing ill effects themselves.

Three-parent Babies
What is mitochondrial donation?

Defective mitochondria in a mother's egg can be replaced with healthy mitochondria from a donor. This will then prevent the harmful mutations being inherited and passed on to future generations.

What are the techniques involved?

There are two different procedures, one carried out before fertilisation and the other after.

Maternal Spindle Transfer (MST) involves first removing the nuclear DNA from a donor egg whose mitochondria are healthy. The "spindle" of chromosomes containing the mother's nuclear DNA is then taken from her egg and inserted into the donor egg.

Three-parent Babies

As a result, the donor egg is left with nuclear DNA from the mother and mtDNA from the donor. This healthy egg is then fertilised and implanted into the mother's womb.

Pro-Nuclear Transfer (PNT) is similar but in this case the mother's egg is fertilised first. Its nuclear DNA is then transferred to a fertilised donor egg, containing healthy mitochondria, whose own nuclear DNA has been removed. This healthy fertilised egg is then implanted.

How safe is mitochondrial donation?

Animal and laboratory experiments suggest that the procedures are safe, but no-one can say that the risk is zero.

Three-parent Babies

There is evidence that small numbers of faulty mitochondria can be "carried over" into the child. They might even replicate in the developing embryo. However, this is not thought to pose a serious risk.

Critics argue that problems might only arise once the procedure is used to create human babies. For instance, replacing mtDNA might have more of an impact on personal traits than had been envisaged.

Unknown epigenetic effects, environmental influences that alter the way genes work, may also have serious consequences for the health of babies, it is claimed.

Has anyone created a three-parent baby?
Three-parent Babies

Just once. New York fertility doctor John Zhang treated a Jordanian woman who carried genes for Leigh syndrome, a fatal mitochondrial disease affecting the developing nervous system.

Following treatment using the Maternal Spindal Technique in Mexico, the boy was born in April this year. So far, he seems perfectly healthy. British expert Dr Dusko Ilic, from King's College London, said the outcome was "revolutionary".



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