British scientists have made a major breakthrough in the battle against diabetes by identifying the genes which raises the risk of getting the condition.
The findings mean there could soon be a test to identify those who could get Type 2 diabetes - of which there are around one million sufferers in Britain.
Many of them developed it because they are overweight or obese.
However experts believe some people are more susceptible than others due to their genetic make up.
Now for the first time researchers have pinpointed the most important genes that heighten the risk of getting type-2 diabetes.
The UK scientists hope it will lead to a test to spot those most at risk so they can take steps to prevent it developing.
It could also lead to new treatments for the condition, which if not properly controlled can lead to serious problems including loss of sight and organ damage.
Lead researcher Professor Philippe Froguel of Imperial College London said: "If we can tell someone that their genetics mean they are predisposed towards Type 2 diabetes, they will be much more motivated to change things such as their diet to reduce their chances of developing the disorder.
"We can also use what we know about the specific genetic mutations associated with Type 2 diabetes to develop better treatments."
The research, published on-line in Nature, is the first time the genetic make-up of any disease has been mapped in such detail.
The team took 700 people with Type 2 diabetes and a family history of the condition, and compared their genetic mutations with 700 healthy people.
The researchers identified four points on sufferer's genetic maps that were linked to their risk of developing the disorder.
They then confirmed their findings by analysing the genetic make-up of another 5,000 people with Type 2 diabetes and a family history of the disorder, to check for the same mutations.
From this they concluded these four points explain up to 70 per cent of the genetic background of Type 2 diabetes.
They also believe one of the mutations might help explain one of the triggers for the condition and so lead to new treatments.
They found sufferers have a particular mutation in a gene involved in transportation of zinc around the body and insulin secretion.
By fixing this problem, they may therefore be able to overcome insulin deficiencies of some people with Type 2 diabetes.
Prof Froguel of the Division of Medicine at Imperial said: "The two major reasons why people develop Type 2 diabetes are obesity and a family link.
"Our new findings mean that we can create a good genetic test to predict people's risk of developing this type of diabetes."
Professor David Balding, study co-author, added: "The task now is to study the genes identified in our work more intensively, to understand more fully the disease processes involved, devise therapies for those affected and to try to prevent future cases."
Dr Iain Frame, Research Manager at Diabetes UK said: "We have known for some time that family history plays a part in whether or not someone might develop Type 2 diabetes.