Question to the Department of Health and Social Care:

To ask the Secretary of State for Health, pursuant to the Written Statement WS132 of 17 December 2014, on mitochondrial donation, what concerns were raised by the expert panel convened by the Human Fertilisation and Embryology Authority regarding the possibility of carryover of a small percentage of abnormal mitochondrial DNA (mtDNA) from the affected oocyte or zygote due to close associations between mtDNA and the karyoplast.

The principle behind the treatment is that the mitochondrial DNA that the child will inherit will be the disease-free mitochondrial DNA of the donor, not the faulty mitochondrial DNA of their mother. Although there is a small possibility that a low level of unhealthy mitochondria may be carried over when the patient’s nuclear DNA is moved from her egg or embryo to the donor’s, evidence continues to be reassuring that carry-over after mitochondrial replacement is very low and unlikely to be problematic. Therefore, the risks of mitochondrial disease being present in the subsequent generation will be low.