Detectable diseases: Some of the conditions which can be detected using low-cost DNA tests

CYSTIC FIBROSIS: Around one in 25 people of European origin are carriers of the gene responsible for CF. Both parents must be carriers, and then a child has a one in four chance of being born with CF. At the moment babies are screened for CF at birth using the heel prick test and the blood DNA analysed.

HUNTINGTON'S: A hereditary disorder of the central nervous system, it usually develops in adulthood. Huntington's disease is caused by a faulty gene on chromosome 4. The faulty gene leads to damage of the nerve cells in areas of the brainand leads to gradual physical, mental and emotional changes.

If you have a parent with Huntington's disease, there is a 50-50 chance of inheriting the faulty gene. Anyone who inherits the faulty gene will, at some stage, develop the disease.

DEMENTIA: Alzheimer's is the most common form of dementia. Medical research has identified four genes that influence disease development, according to the Alzheimer's Society. Three of these genes affect younger people, and one affects older people. Vascular dementia is the second most common form of dementia. There are a number of very rare forms of the disease that are caused by genetic mutations. Anyone who is worried about inheriting a form of dementia and who has a relative with the condition should speak first to their GP. If someone has more than one family member affected by early onset dementia they may be referred to a regional clinical genetics department.

HEART: Certain heart conditions, such as cardiomyopathy, are inherited. Scientists have also identified a genetic flaw which increases the risk of heart disease and heart attacks. In 2007, researchers found that up to one in four white people carries the section of DNA which increases the risk of heart disease by around 40 per cent.

PARKINSON'S DISEASE: In Parkinson's there is a loss of nerve cells in part of the brain.

These cells are responsible for producing the chemical dopamine, which allows messages to be sent to the parts of the brain that co-ordinate movement. Scientists have so far identified nine genes linked to Parkinson's.