Britain on 3 Feb 2014 became the first country in the world to allow ‘Three Parent – In Vitro Fertilisation (TP-IVF)’ or ‘Three Parent Babies’. This technique will help couples with mitochondrial diseases, an incurable conditions passed down the maternal line that affect around one in 6,500 children worldwide. But critics say the technique will lead to the creation of genetically modified ‘designer babies’.
The treatment is known as TP-IVF because the babies, born from genetically modified embryos, would have DNA from a mother, a father and from a female donor. Under current UK law, genetically altered embryos cannot be implanted into a woman. But in this case fertility clinics will be given license for TP-IVF.
What is the benefit of TP-IVF?
A small number of children each year are born with faults in their mitochondrial DNA which can cause diseases. Mitochondria are small structures present inside cells and provide energy. They have their own set of 37 genes which are separate from the 25,000 genes present in nucleus and does not affect human characteristics such as hair or eye colour, appearance or personality traits.
How do the faulty mitochondria affect people?
The parts of the body that need most energy are worst affected: the brain, muscles, heart and liver. Faulty mitochondria have also been linked to more common medical problems, including Parkinson’s, deafness, failing eyesight, epilepsy and diabetes. There are no cures for mitochondrial disorders.
How are mitochondrial disorders passed on?
Only mothers pass mitochandria on to their children. Because egg cells contribute nucleus as well as rest other cellular component including mitochondria whereas sperms contribute only nucleus during fertilization process.
How TP-IVF could prevent the mitochondrial diseases?
Scientists have developed two techniques to stop mitochondrial diseases being passed from mother to child.
The first is called mitochondrial spindle transfer (MST). In this, doctors use standard IVF procedures to collect eggs from the mother. They take the nucleus from one of the eggs and drop it into a healthy donor egg that has had its own nucleus removed. The reconstituted egg contains all the normal genes from the mother, but her faulty mitochondria are replaced by those from the healthy donor. The egg is then fertilised with the father’s sperm. The resulting embryo has the usual 23 pairs of chromosomes that hold the mother and father’s DNA, but the 37 mitochondrial genes, about 0.2% of the total, come from a third person, the donor.
The second procedure is called pronuclear transfer. It is similar to MST, but both the mother’s and donor’s eggs are fertilised first with the father’s sperm. Before the eggs divide into early stage embryos, the parents’ chromosomes are removed from the mother’s fertilised egg and placed into the donor egg, which has had its own chromosomes removed.
Is mitochondrial transfer safe and effective?
Both procedures have been tested in animals and resulted in healthy offspring. Good results have also been seen in human cells, but treated embryos have not been implanted into a woman to achieve a pregnancy. A review of work on mitochondrial transfer by independent scientific panel concluded there was no evidence the procedures were unsafe.
What objections do people have to the TP-IVF procedure?
Mitochondrial transfer passes on genetic changes from one generation to another. That raises ethical concerns because any unexpected problems caused by the procedure could affect people who are not yet born. Mitochondria are not completely understood, and the DNA they hold might affect people’s traits in unknown ways. The Catholic church opposes because a fertilised egg from the mother is destroyed in pronuclear transfer process and mitochondrial transfer dilutes parenthood.
Is ‘three-parent’ babies a good description of children born to the procedure?
Three-parent baby is misnomer. Women who donate their mitochondria would remain anonymous and have no legal rights over the child. On a genetic level the donor only contributes mDNA, less than 0.2% of the total genetic material.
Will this change in law allow ‘designer’ babies?
Designer baby is a concept of modifying human characteristics such as eye, skin and hair colour and other defining traits by altering nuclear DNA or gene. The procedure of TP-IVF does not change this nuclear DNA. The ban on altering nuclear DNA remains in place.