When she was just three months old, doctors noticed that Kirthana Balachandran suffered from tiredness. She was soon diagnosed with beta thalassaemia, a blood disease that makes people weak and exhausted.

Balachandran explains: "Sometimes I have muscle pain, back pain and I can even feel breathless or have palpitations when I walk uphill." Every three to five weeks she has to get a blood transfusionTransferring donated blood or other liquids into the body of a patient. . As a result her body is covered in scars. She worries about what will happen if too much ironA common metal. It melts at 1,538C. Rain made of iron would be deadly. builds up from the injections.

But now a miracle cure might be at hand. Britain's NHSThe National Health Service, the publicly funded healthcare system in the UK. The NHS was founded in 1948. has approved the first geneA gene is the basic unit of heredity.-editing treatment. The health service's chief executive Amanda Pritchard calls it "a historic moment".

Gene therapy is a medical approach that treats illnesses by changing the genetic problem that causes them. The first successful approach, gene addition, sees doctors place a new gene into cells to fight a disease.

Gene editing is more complex. The new technique, known as CRISPRCRISPR-Cas9 allows scientists to remove, add or alter sections of DNA with ease and simplicity. ,¹ involves using molecular-sized scissors to alter existing DNADeoxyribonucleic acid is the material in an organism that carries genetic information.. It could, for instance, turn on a gene that does not function, or turn off one that is working incorrectly.

For thalassaemia, the stem cellsUnspecialised cells that have the ability to develop into different types of cell. that do not work are extracted and altered.² The patient has to undergo chemotherapyA treatment for cancer that uses powerful drugs to kill cells. to kill off the old cells before new ones can be put in.

This process has already succeeded. Abdul-Qadeer Akhtar took part in clinical trials before the treatment was approved. He has taken up boxing and started to travel more freely. He said: "My overall health and quality of life have significantly improved. I'm eager to embrace life to the fullest."

There are risks associated with gene therapy. In 1999, a young American called Jesse Gelsinger died after his body reacted against genetic treatment for a rare liver problem.

Another test begun the same year looked to restore an important immune systemThe network of cells, organs and proteins that defend the body from infection. cell in children. It seemed to work well. But five of the children developed leukaemiaCancer of the white blood cells. . One of them died.

Doctors have learnt from these tragedies. But gene therapy raises further moral problems. It comes with an enormous price tag. One treatment typically costs around £1.6m.³

In countries where people pay directly for healthcare, the surgery might be out of reach for those who need it. In countries with it, it could put intense strain on health services. A two-tier system could develop, where only the richest can benefit from the cures.

Removing disease is one thing. But what if you alter genetics to make people "better"? It could enable a new generation of eugenicsThe idea that human beings should be improved through genetic engineering. In the past, eugenics has generally involved killing people who are deemed "inferior"..⁴ The super-rich could edit their babies to make them stronger and smarter than others. Differences could be edited out to create "perfect" humans.

Some fear scientists could tamper with genes to create super-soldiers who run on four hours of sleep, barely feel pain and have immense physical strength. This can be achieved with current technology. Expert Fyodor Urnov says: "You don't need a large lab operation. You just need the ill will."

Is this a dangerous path?

Yes: It can achieve some good in the short term. But it is a very slippery slope. Soon we could have genetic super soldiers, designer babies and design-your-own child schemes. This is against nature.

No: Scientists have always been capable of doing dreadful things. But they mostly manage to restrain themselves from the worst. There is no reason things will be any different with gene editing.

Or... There are always risks, but the work being done now is mostly positive. But new dangers are always possible. We should take care to ensure all new developments are regulated and monitored.

FOR YOUR SUMMER READING CHALLENGE CLUE GO TO STEP SIX IN THE SIX STEPS TO DISCOVERY BELOW.