Three-parent babies
Jack Teh In the UK alone, around one in 200 babies born has various forms of dysfunctional mitochondria; it is a vital organelle that generates chemical energy for the cell 1 . The existence of dysfunctional mitochondria in the cells will cause mitochondrial disease, which is a group of disorders that will lead to heart failure, visual problems, neurological problems, muscle weakness and even death 2 . Currently, there is no cure for this genetically inherited disease. However, scientists proposed that they could use healthy mitochondria from another donor woman to replace the unhealthy ones from the mother’s egg to prevent severe genetic defects on the baby 3 . Since mitochondria contain their own mitochondrial DNA, the baby will have DNA from three people; thus, the baby is called the ‘three-parent baby’. The technique called three-parent in vitro fertilization (TPIVF) is currently banned in all European countries and the United States, but there is possibility that UK will be the first country to legalize this technology. In this essay, I will write about three-parent IVF including a case study, as well as giving arguments on both sides addressing the implication of legalizing three-parent IVF. All cells in the human body except reproductive cells have 23 pairs of chromosome. Each chromosome contains hundreds or even thousands of genes. One of each pair of chromosomes is inherited from each parent, meaning that there are two copies of each gene in each cell. Mitochondria, which contain their own mitochondrial DNA (mtDNA), are inherited exclusively from the maternal side because even though the sperm’s mitochondria enter the egg, they are almost always destroyed by autophagy (cell degradation) 4 . Therefore, any dysfunctional mitochondria will only be passed from the mother to the baby. Mitochondrial disorder is caused by mitochondrial DNA mutations that happen regularly due to the lack of error checking capability that normal nuclear DNA has; the disorders may occur randomly and relatively often 5 . If some of the mtDNA copies inherited from the mother are defective, the faulty copies will divide in the cells of the embryo. Not only are mitochondria involved in many of the important internal functions of the body, such as generating most of our cells’ chemical energy and signalling between cells leading to cellular differentiation or cell death, but also controlling the cell cycle and cell growth 6 . As the number of defective mitochondria reaches a certain level, the physical deficiencies will become apparent. Sharon Bernadi, from Sunderland, suffers from Leigh’s disease and lost all seven of her children three years ago 7 . During the first three pregnancies, she felt perfectly well but her three babies died hours after birth. It was suspected by doctors that the deaths were not coincidental; she wasn’t diagnosed with Leigh’s disease until after her fifth baby had died within hours. However, her fourth child, Edward, who fortunately survived, was also diagnosed of Leigh’s disease when he had his first seizure at the age of four. Everything seemed like a miracle for Edward, but he had to be monitored and taken care constantly. Edward fought through all the years with the disease and survived until he was 21 8 . Leigh disease is a common example of mitochondrial disease. It is a rare, inherited progressive neurodegenerative disorder that usually presents in infancy or early childhood; it particularly affects the brain and the central nervous system 9 . Severe muscle and movement problems are common in Leigh disease. Babies would normally die in a couple of years usually due to respiratory failure. Some affected individuals develop hypertrophic cardiomyopathy; this is when the muscle wall of the heart becomes thickened and forces the heart to pump blood harder 10 . Sharon was desperate to have normal children as the other mothers would want but her dream never came true. It sparked her urge to find a cure so that her children would not suffer from Leigh’s disease anymore.
1 Mundasad, 2014 2 Knapton,2014 3 Gallagher, 2014a 4 Mitochondrion, Wikipedia, 2014 5 Mitochondrial disease, Wikipedia, 2014 6 Mitochondrion, Wikipedia, 2014
7 Dicker, 2012 8 Banerji, 2012 9 Ibid. 10 Leigh syndrome, Genetics Home Reference, 2011
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