Frequently Asked Questions

There are a number of reasons why you might have a higher chance of being a carrier of a particular genetic condition or chromosome rearrangement. These include the following:

• Most carriers are healthy, do not have any symptom of the disease and there are no affected relatives, either. However, being a carrier for a genetic disease may increase the risk of having affected children. Genetic counselling will help to properly ascertain this risk and to discuss what your options are.
• Someone in your family has a genetic disease, recessive, X-linked, or chromosome rearrangement.
• Someone in your family has found out that they are a carrier of a particular recessive condition, X-linked condition, or chromosome rearrangement.
• Your child has been diagnosed with a genetic disease.
• You have a particular ethnic background which increases the likelihood of you carrying a particular genetic condition. Examples of this include sickle cell disease in people of Afro-Caribbean descent, beta-thalassaemia in people of Mediterranean descent, cystic fibrosis in people from Western Europe, and Tay-Sachs disease in people of Ashkenazi Jewish descent. These conditions are more prevalent in these particular ethnic groups, but can still occur in others.

Even if none of these reasons apply to you, you may decide to have a carrier test because your partner knows he or she is a carrier of a particular recessive condition. In this case the results of your test will help you to find out if your future children are at an increased risk of having the condition.

Our bodies are made up of trillions of cells. Most cells contain a complete set of genes, which act like a set of instructions for how our bodies work and grow. Genes are also responsible for many of our characteristics, such as eye colour, blood type or height. We all inherit two copies of most genes, one set from our mother and one from our father. That is why we often have similar characteristics to our parents.

Genes are located on small thread-like structures called chromosomes. Usually we have 46 arranged in 23 pairs, with one from each pair inherited from our mother and the other from our father.

Sometimes, there is a change (mutation) in one copy of a gene which stops it from working properly. This change can cause a genetic condition because the gene is not communicating the correct instructions to the body.

A genetic test involves the analysis of a blood or tissue sample to identify whether there is a change in a particular gene or chromosome in that individual.

Reasons to undergo genetic testing include the following:

• You have a child with learning difficulties, developmental delay or health problems, and your doctor has considered a genetic disease.
• Your doctor has diagnosed a possible genetic condition in you and wants to confirm the diagnosis.
• There is a history of genetic disease in your family, and you want to know your risk of developing it in your lifetime.
• Your partner has a genetic disease in the family, which can be passed on to your children.
• Other tests during your pregnancy (such as ultrasound or blood test) have shown an increased risk of your baby having a genetic disease.
• You had a miscarriage or a stillbirth.
• You have several close relatives who have developed certain types of cancer.
• You have an increased risk of having a child with a specific recessive genetic disease because of their ethnic origin. Examples include sickle cell anaemia (or sickle cell disease) in people of Afro-Caribbean descent, beta-thalassaemia in people from southern Europe and around the Mediterranean, cystic fibrosis in people from Western Europe, and Tay-Sachs disease in people of Ashkenazi Jewish descent. These diseases are more prevalent in these populations, but can still occur in others.

A predictive genetic test can provide information about the likelihood of a person developing a specific condition, usually at a later stage in life. The test is usually performed on a blood sample.

The blood is analysed in a genetics laboratory to see if there are any changes in a particular gene or genes related to a disease. 

If there is a known genetic condition in your family and the changed gene that causes that condition is known, you might be able to have a predictive test to see if you have inherited the changed gene. This information is particularly useful for conditions that can be prevented or for which the symptoms can be effectively treated. For conditions that can neither be prevented, nor the symptoms effectively treated, you might still want to have the test for the following reasons:

• You want the information to help you make decisions about having children, or to tell you more about your own children’s risks.
• You believe that knowing more about your chances of getting the disease will help you make important life decisions, including decisions about your healthcare.
• You are the type of person that prefers to know more about your own future and prefers to live with certainty than with uncertainty.