Alzheimer’s disease

It has been discovered that there are defective gene clusters present in those suffering with this disease which may have been passed on genetically or could be due to other, as yet, unknown factors.

Angelman syndrome

Developmental delay and nervous system problems caused by a mutation in the UBE3A gene, which is passed down from the mother to the child. Non-fatal but seriously debilitating.

Asthma

There is evidence that asthma can be caused by defective genes passed on through conception. This can lead to poor quality of life and is one of the most rapidly growing conditions affecting children in the world today.

Breast cancer

This can be fatal if not caught early enough and treated. It can lead to a double mastectomy (removal of both breasts) causing much distress to the sufferer. The gene responsible has now been isolated and can be tested for.

Canavan disease

A degenerative condition that leads to death mainly affecting Ashkenazi Jews. A child born with this condition suffers from severe brain erosion and it is often fatal before the child reaches its second birthday.

Cancer

It is now known that many forms of cancer are inherited through genes. If cancer exists within the family tree of either parent a test is advised before conception.

Cardiovascular disease

Apart from lifestyle factors there are genes that can be passed on that can cause this disease or the factors that can lead to it such as high blood cholesterol and hardening of the arteries.

Corneal dystrophy

Incurable eye disorder which causes scarring of the cornea of the eye which often leads to severe visual impairment.

Cystic fibrosis

Incurable defective genes from both parents which causes repeated respiratory infections, trouble breathing, severe digestive problems (in turn preventing weight gain and normal growth), diabetes and liver failure. Life expectancy 40 years.

Diabetes

This can cause a lifetime of dependence on medications and a careful watch on the diet. It can also lead to complications such as blindness, kidney failure, heart disease and limb amputation due to nerve damage and poor blood circulation.

Down’s syndrome

This can be caused by a failure of the 21st chromosome to separate during egg or sperm development and is associated with conception in older women. The condition can also be passed on genetically through defective sperm or egg development carrying the extra chromosome 21 material even if the parents show no other sign of the condition.

Dwarfism

This is usually caused by a genetic disorder; achondroplasia which is a mutation on chromosome four.  It can be screened for and avoided.

Fragile X syndrome

The most common cause of inherited mental retardation.

Huntington's disease

Incurable genetic disorder that causes the brain's nerve cells to progressively and irreparably break down.

Muscular dystrophy

This debilitating condition causes muscles to be easily damaged and become weaker over time. It can affect both voluntary muscles like those in the limbs and involuntary ones such as in the heart. Sufferers usually end up wheelchair bound.

Neurofibromatosis

Incurable genetic disorder which causes the growth of tumours throughout the nervous system.

Polycystic kidney disease

Causes numerous noncancerous cysts to develop on the kidneys which can lead to a high blood pressure, abdominal pain, kidney stones and even kidney failure. It may not manifest itself for many years even into adulthood.

Sickle cell disease

This is caused by a mutation in the gene that contains the instructions for creating haemoglobin which causes hypertension, infections, stroke, blindness and potentially fatal organ damage. Both parents must pass on a copy of the mutated gene for the disease to develop in a child.

Tay-Sachs disease

An incurable and serious genetic disorder that leads to the destruction of a child's neurons, eventually ending in death, often by age 4.

Thalassaemia

This is the absence of, or errors in, genes responsible for production of haemoglobin, a protein present in the red blood cells. Each red blood cell should contain between 240 and 300 million molecules of haemoglobin.  If the foetus is affected by alpha thalassaemia major it may have a very low chance of survival and if it does could have a very poor quality of life.

Usher’s syndrome

This incurable syndrome is caused by a mutation in any one of 10 genes resulting in a combination of hearing loss and visual impairment and is a leading cause of deaf blindness.