A carrier is someone who has one faulty copy of a gene that is associated with a recessive genetic condition. Carriers still have one working copy of the gene which can compensate for the faulty copy. They do not usually develop symptoms of the particular genetic condition, but can pass the faulty copy of the gene on to the next generation and may have an increased chance of having an affected child. Research has shown that more than 80% of people are carriers of at least one genetic condition, often without knowing it.

Carrier screening is a type of genetic test that involves analysing an individual’s DNA to determine if they are a carrier of a range of autosomal recessive genetic conditions. In biologically female individuals, carrier screening will also analyse genes associated with X-linked recessive conditions. This information can be useful in understanding the risk of having a child with a genetic condition

Carrier screening is available to anyone who wants to learn more about their risk of carrying a genetic condition. Some genetic disorders occur more often in certain races or ethnic groups. For example, Gaucher disease typically affects people of Ashkenazi Jewish ancestry, and sickle cell disease often affects people of African descent. However, these conditions are not restricted to these groups, and anyone can be a carrier.

Not at all! Carrier screening is available to anyone who wants to learn more about their risk of carrying a genetic condition, whether you have a partner or not. If you are single and are considering using donated sperm/eggs, you may wish to have carrier testing of conditions your donor is known to be a carrier of.

It is generally recommended to have carrier screening before you are looking to expand your family, but carrier screening can be performed at any time. If you (or your partner) are pregnant and wish to have carrier screening, we would recommend performing the test as early as possible.

We may recommend that you have a consultation with one of our genetic counsellors so we can better understand your situation, and let you know whether carrier screening or a different type of genetic test may be appropriate.

An individual who is affected with an autosomal recessive condition has a disease-causing variant in both copies of a particular gene, and therefore has two faulty copies. Typically, they have inherited one variant from each biological parent. Having only one faulty copy (and a second working copy of the gene) means that someone is a carrier of the condition. Carriers usually do not have any symptoms, and are often unaware that they are a carrier.

Some examples of autosomal recessive conditions include cystic fibrosis (CF), sickle cell anaemia, and phenylketonuria (PKU).

If both biological parents are carriers of the same autosomal recessive genetic condition, in each pregnancy there will be a 25% or 1 in 4 chance of having an affected child, a 50% or 1 in 2 chance that the child will be a carrier, and a 25% or 1 in 4 chance that the child will not inherit any faulty copies of the gene.

An individual who is affected with an X-linked recessive condition has a disease-causing variant in a gene on the X chromosome. These conditions typically affect biologically male individuals, who have one X chromosome and one Y chromosome, while biologically female individuals have two X chromosomes. As females have a second working copy of genes on the X chromosome, they typically do not develop symptoms of X-linked recessive conditions and are considered to be carriers. Males do not have a second working copy of genes on the X chromosome to compensate for the faulty copy, and will therefore typically show symptoms.

Some examples of X-linked recessive conditions include haemophilia, Duchenne muscular dystrophy and Fragile X syndrome.

For a carrier female, in each pregnancy there will be a 25% or 1 in 4 chance of having an affected male, a 25% or 1 in 2 chance of having a female child who is a carrier, and a 50% or 1 in 2 chance that the child will not inherit the faulty copy of the gene.

For an affected male, there will be a 25% or 1 in 4 chance of having a female child who is a carrier, and a 75% or 3 in 4 chance that the child will not inherit the faulty copy of the gene. Affected males cannot pass on a faulty gene on the X chromosome to their sons, as they always pass on their Y chromosome rather than their X chromosome.

After providing your details and paying for your test, you will be able to schedule an appointment with one of our genetic counsellors. In this session, the genetic counsellor will discuss the testing process in more detail including the benefits and limitations, possible results and implications, and address any questions or concerns you may have. Assuming you are happy to proceed with the testing, the genetic counsellor will send you our test requisition form to review and sign electronically.

You will receive your test kit in the post – this will contain a DNA sample collection kit and a pre-paid returns envelope. DNA can be extracted from a saliva sample collected in a specialised collection tube.

Once your saliva sample has been received by our genetics laboratory, the DNA will be extracted and sequenced. Scientists in the lab will analyse the sequencing data to see if any disease-causing variants are present in the requested genes. The report is typically available within 20 working days.

No, carrier screening and non-invasive prenatal testing (NIPT) are different tests. NIPT is a genetic test that is performed during pregnancy and involves analysing small fragments of DNA that are circulating in a pregnant mother’s blood, to assess whether a baby has an increased chance of having a chromosomal condition such as Down syndrome.