Can I be a carrier of a genetic disease?
There are a number of reasons why you might have an increased chance of being a carrier of a particular genetic condition or chromosome rearrangement.
- Someone in your family has a recessive condition, X-linked condition, 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.
- You have a child who has a recessive condition, X-linked condition, or chromosome rearrangement.
- You have a particular ethnic background which means you are more likely to be a carrier of a particular genetic condition. Examples of this include sickle cell in people of Afro-Caribbean descent, beta-thalassaemia in people of Mediterranean descent, and Tay-Sachs in people of Ashkenazi Jewish descent. These conditions are more prevalent in these particular ethnic groups, but may occur in others.
Even if none of these reasons exist, 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.
What are Genes and Chromosomes?
Our bodies are made up of millions of cells. Most cells contain a complete set of genes. Genes act like a set of instructions, controlling our growth and how our bodies work. They are also responsible for many of our characteristics, such as our eye colour, blood type or height. We have thousands of genes. We each inherit two copies of most genes, one copy from our mother and one copy from our father. That is why we often have similar characteristics to both of them.
Genes are located on small thread-like structures called chromosomes. Usually we have 46 chromosomes in most cells. We inherit one set of 23 chromosomes from our mother and one set of 23 chromosomes from our father. So we have two sets of 23 chromosomes, or 23 pairs.
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.
What is a Genetic Test?
A genetic test can help identify if there is a change in a particular gene or chromosome. This is typically a blood/tissue analysis.
Genetic testing may be performed due to various reasons, such as:
- You have a son with learning difficulties, developmental delay or health problems, and that 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 genetic disease in your family, and you want to know if you have a high risk of developing it throughout your life.
- One of the members of a couple has a genetic disease in the family, which can be passed to on to your children.
- You have performed other testing during pregnancy (such as ultrasound or blood test) that showed an increased risk that your baby has a genetic disease.
- You had a miscarriage or a stillbirth.
- You had 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 anemia (or sickle cell disease) in African-origin people, thalassemia in people of southern Europe and around the Mediterranean, cystic fibrosis in people from Western Europe and the Tay-Sachs disease in Ashkenazi descent people (Jews from central Europe). These are more frequent disease in certain populations, but may occur in others.
It is not always necessary for the physician to request a genetic test. He may diagnose a genetic condition simply with a clinical examination, or advise you on a recurrence risk by analyzing a detailed family history.
What is a predictive genetic test?
A predictive test can provide information about whether or not a person will develop or is likely to develop 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 the 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. You might want to have a test if:
. the condition can be prevented or its symptoms effectively treated, or if
. the condition can neither be prevented, nor its symptoms effectively treated, but:
- You want the information to help with decisions about having children, or to tell you more about your own children’s risks.
- You believe that knowing more about your chance of getting the disease will help you to 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.