Genomic Testing
This fact sheet explains a new form of genetic testing called genomic testing which is used to find
causes of genetic conditions.
What are chromosomes and genes? Each body cell contains
chromosomes, which store genetic information. These genetic
instructions control the development of all organs, such as the
brain, heart and kidneys and how they work. Body cells usually
contain 46 chromosomes, arranged as 23 pairs according to their
size. One of each of these pairs is inherited from our father and
the other from our mother. The first 22 pairs of chromosomes are
rd
similar in men and women. The 23 pair is called the sex
chromosomes. These are called XX in women and XY in men.
The picture shows a cell containing chromosomes. One
chromosome is enlarged and shows that it consists of DNA from
which genes are made.
There are about 20,000 genes in each cell. All of these genes make up the “genome” in the cell. Just
like the chromosomes, the genes also usually come in pairs, one from each parent. Genes contain
information for the cells of the body to function in the form of code words that the cell “reads”. Each
gene has a specific function, however the function of all genes is not yet known. Variations in genetic
information in different people can occur which is why we are all unique. Some variations are harmless
but others can make a gene not work (called a mutation). Mutations may be missing or extra
segments of DNA within a gene or a variation in the DNA code. Some mutations do not cause a
genetic condition by themselves but only when environmental factors are added. This combination
may increase the chance of a genetic condition developing. Identifying mutations may help to find the
cause of the genetic condition in you or your family which may be important for you, the affected
individuals and other blood relatives. Genetic mutations can be inherited from one or both parents or
may occur for the first time in a person before or during their conception.
Why is genomic testing done? Previously, testing to look for mutations involved examining only one
gene at a time. It could therefore take many years to identify the cause of the condition, especially if
the condition is one that may be caused by mutations in one of several genes. It is now possible to
test all 20,000 genes at the same time by genomic testing. This means that the cause of a genetic
condition may be detected within a shorter time period.
Which genes will be tested? Firstly, genes that are already known to be involved in directly causing
or increasing risk for the specific genetic condition in you or your family will be tested (gene panel
testing). If no gene mutations are found, or if you and your doctor choose to go directly to testing all
genes first, then genomic testing of all the 20,000 genes will occur.
What are the possible outcomes of testing by genomic testing?
1. A gene mutation is found that is the cause of the genetic condition. Your doctor will discuss
these results with you and the meaning of the results for your blood relatives. It is your choice
whether you will inform your relatives to give them the opportunity to participate in genetic
testing. Your family will not be approached by your doctor or genetic counsellor unless you
give permission or it is required by urgent medical circumstances.
2. One or more gene variations are found where the significance is not clear. Additional testing of
other blood relatives may help to determine if the result is relevant in causing the genetic
condition.
3. One or more genetic variations are found which are known to be harmless and not to cause
genetic conditions. These will not be discussed with you.
4. Rarely, one or more genetic mutations that are not related to the genetic condition being
investigated are found by chance. These are called co-incidental findings. An example of this
could be a gene mutation associated with an increased risk of a serious health problem in you
or your blood relatives. These results will be assessed by an independent committee of
experts in collaboration with your doctor or genetic counsellor. The findings will be discussed
with you if they could have important consequences for you or other family members.
5. No gene mutations are found that could explain the genetic condition. In this situation, more
testing may be available in the future. The timeframe for this is unknown.
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Are there any other results of genomic testing that will not be reported? We all have many
mutations in single genes that are not thought to cause disease. A disease may occur when both
copies of such a gene do not function. Although these single gene mutations may be identified by
genomic testing, they will not be confirmed or reported by the laboratory as they are not currently
known to cause health problems in the person being tested. Not all gene changes that influence
diseases have been identified.
What is the impact of increasing understanding of genetic information on the interpretation of
genome testing? Knowledge of the function of genes and genetic conditions is increasing rapidly and
this may mean that interpretation of results obtained today could change in time. It is possible that you
may be contacted in the future if additional information becomes available regarding the results of
genomic testing but the timeframe in which it could happen are uncertain.
What is required for the genomic testing? Your doctor will explain the testing and obtain written
consent prior to any testing being done. A blood sample of 5-20ml (1-2 tubes) will be required from the
person being tested from which DNA will be extracted. In some cases it may also be necessary to test
blood samples from other blood relatives e.g. parents of an affected child to help in understanding the
results. You have the right at any time to withdraw your consent, without affecting the quality of your
treatment.
What will happen to the extracted DNA? When the testing is completed your DNA is stored in the
laboratory according to the current Australasian guidelines. Your DNA sample will not be sent to other
laboratories for research studies unless you give prior permission and the study is also approved by
the hospital ethics committee.
Why is it important that genomic testing results may be used for research? As well as aiming to
provide information for you and your family, the information obtained from genomic testing is important
for increasing knowledge and understanding of genetic mutations and the causes of diseases. It is
therefore important for scientists and doctors to be able to learn about gene variations that have been
identified in your sample. If you give your permission, a genome wide analysis of all or most of the
genes in your DNA sample will be performed as part of genomic research to study links to many
diseases and conditions.
In order to allow researchers to share test results, the National Institutes of Health in the United States
(NIH) and other central repositories have developed special data (information) banks that collect the
results of genome testing. If you agree, the NIH and other data banks will store your de-identified
genetic information and make it available to other qualified researchers to study further. Research
using genome information is important and so the databank will provide study data for researchers
working on any disease. Qualified researchers who can access these databases can be from the
government, academic, commercial or non-commercial organizations. It is unlikely that there will be
risks to your privacy and confidentiality by sharing your genome analysis with these databanks;
however, we cannot predict how genetic information will be used in the future. The information would
be de-identified and sent with a code number attached. Any identifiable information would never be
given to the database. There are many safeguards in place to protect your information while it is
stored in repositories and made available for research.
There is a very small chance that your genetic information could be shared with others by mistake or
that you could be identified from the sample if someone has another sample from you. If it was then
linked with a medical condition, this could affect your ability to get or keep some life insurance
products. There is also the chance that data could be released to the public, employers, or law
enforcement agencies. If family members were to see this information it could also affect them and in
some instances, this could hurt family relationships.
You will not receive any results from allowing your data to be placed in these databases unless it is
considered medically relevant. No direct benefit can be promised from your participation however the
inclusion of your genome data will contribute to scientific knowledge about genetic problems and
medical conditions. You can withdraw your consent at anytime if you do not wish your data to be
present in these databases. There will be no consequences for withdrawing consent. However, data
that has already been sent to researchers cannot be retrieved from those researchers.
What if I have any other questions? If you have any other concerns or questions, please contact
your doctor or genetic counselor.
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