DNA (deoxyribonucleic acid) carries the genetic information in the body’s cells. A gene is a distinct portion of a cell’s DNA. Genes are packaged in bundles called chromosomes. A genetic disorder is an illness or condition caused by abnormalities in genes or chromosomes.
There are many types of genetic tests or screenings available, the most common being:
• Gene carrier testing to examine a person’s DNA to ascertain if they are a carrier of a faulty gene or carry a faulty gene which can be subsequently passed on to future generations.
• Chromosome testing to examine for the presence of abnormal chromosomes most commonly found in and associated with the unborn baby
Gene carrier screening
Many Genetic Diseases Are Preventable
Each year millions of healthy parents are taken by surprise when their children are born with life-threatening genetic disorders. These parents are carriers: healthy individuals who nevertheless have a mutant version of a critical gene. If the results show that both prospective parents are carriers of a condition, they could choose to have IVF and screen their embryos, so that only healthy ones are implanted in the womb. Other options include genetic testing during pregnancy, or adoption. Some couples armed with all the facts, then have the choice to choose and some may decide to terminate the pregnancy.
Testing Allows Prevention
The new medical consensus from the Human Genome Project states ”There is no legal, ethical or social reason why people should not be screened for genetic mutations before they start a family”. Screening could prevent babies being born with life threatening conditions such as cystic fibrosis and sickle-cell disease. Many families with a known risk of an inherited disease are already offered testing.
This my my: dna would suggest that every adult should be offered the chance of having a genetic test ideally before pregnancy. Early testing is the only way to know if your future generation will be at high risk, and to allow parents and doctors to take specific actions to conceive a healthy child.
1 in 20 people have a faulty gene(s) which increases their chance of having a child with a serious disorder
A person with a gene disorder will carry two copies of a mutated gene. However, about 1 in 20 people carry a single faulty gene and will show no signs of the disorder but can still pass it on to subsequent generations. Two unaffected people who each carry one copy of the same mutation have a 1 in 4 chance of having a child affected by the disorder. Common disorders include Cystic Fibrosis, Fragile X Syndrome and Spinal Muscular Atrophy.
A simple carrier screening test can be performed to rule out this unknown factor for your future reassurance. This kind of screening can be performed prior to conception or as part of your pregnancy care. If a couple are found to be carriers, prenatal diagnostic testing can be performed to see if their baby is affected.
Carrier screening is a one-off test for either one person or a couple. If you are not found to be a carrier you cannot pass on a faulty gene.
For most disorders a child is affected if both parents are carriers and both pass on their faulty gene e.g. Cystic Fibrosis. For other disorders it is sufficient for the mother to be a carrier but the fault worsens when it is passed on e.g. Fragile X syndrome.
Despite the high risk to carriers, most affected children are born into families with no history of the disorder. This is because couples do not think about screening and thus they are unaware that they both carry the same fault gene.
How do I screen?
The test is simple on your part, a blood sample is taken or a saliva sample given and sent to one of our expert laboratories. The DNA is extracted from the sample and the laboratory checks the DNA strands to see if there are any abnormal changes or mutations.
Should I screen?
Those considering screening need to make a number of decisions: if to be screened at all; if screened and a positive result is given whether to have preconception counselling or if pregnant whether to have a prenatal diagnostic test; and finally if your pregnancy is found to be affected whether to continue with your pregnancy.
It is important to remember that the vast majority of screening tests are normal. Screen results can provide a sense of relief from uncertainty and help you make an informed decision about managing your future and your future generations. A positive result can direct you towards available diagnostic testing. Screens can be used for couples thinking about having a baby to ensure that their baby is healthy right from the very start.
Genetic testing is voluntary. Because testing has both benefits and limitations, the decision about whether to be tested is a personal and complex one. At this is my: dna a genetic counsellor can help by providing information about screening and discuss the social and emotional aspects of testing.
What if we are both found to be carriers of the same gene mutation?
If you are thinking of starting a family and found to be a carrier it is worth considering telling your partner to be screened if not already done. If you are subsequently both found to be carriers of the same gene mutation then pre-conception screening should be considered.
If expecting and you are both found to be carriers for the same gene mutation it is important to remember that there are more chances are that your baby will still be unaffected but invasive prenatal diagnostic screening should be considered, i.e. amniocentesis or chorionic villus sampling. Pregnancy genetic screening will not tell you if your baby is affected, it will only give you a risk. Screening aims to provide information to help decide whether prenatal diagnosis is warranted.
For more information about screening, please refer to our Screening Options Page
Tests available at this is my:
Chromosome Screening in Pregnancy
|Please see our this is my: baby pregnancy section|