Is this a dangerous path? A huge breakthrough might transform the lives of those with certain blood disorders. But some worry about the medical and moral side effects.
UK gene therapy at £1.6m per patient

Glossary
NHS - The National Health Service, the publicly funded healthcare system in the UK. The NHS was founded in 1948.
Gene - A gene is the basic unit of heredity.
CRISPR - CRISPR-Cas9 allows scientists to remove, add or alter sections of DNA with ease and simplicity.
DNA - Deoxyribonucleic acid is the material in an organism that carries genetic information.
Stem cells - Unspecialised cells that have the ability to develop into different types of cell.
chemotherapy - A treatment for cancer that uses powerful drugs to kill cells.
Clinical trials - Studies by experts that test whether a new medicine or treatment works and is safe.
Eugenics - The idea that human beings should be improved through genetic engineering. In the past, eugenics has generally involved killing people who are deemed “inferior”.