Frequently asked questions
We offer a selection of FAQs in response to inquiries on gene tests-related issues.
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Genes are the parts of our DNA that contain the instructions needed for a cell to make proteins. These instructions are in the form of a code using four types of molecules called nucleotides. These are Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). Depending on the order in which these molecules are arranged, different proteins can be produced by different genes.
All human beings have the same set of about 20,000 genes. These are present in our DNA in almost every single cell in our bodies. The specific sequence of As, Ts, Cs and Gs that make up each gene can be "read" by a cell and "translated" into the corresponding protein.
Proteins produced from these genes perform almost all the functions of our body — they build muscles, skin, bones and all organs; they maintain the shape and structure of different cells; they digest nutrients and deliver molecules to different destinations.
Sometimes the sequence that makes up a gene can carry a “mistake” in it, changing the sequence of the gene. Such sequence changes in the genes are also referred to as variants.
Some examples of these changes include:
- Replacement of one part of the sequence with another (like a spelling error)
- An insertion/deletion of a small part of the sequence
- An insertion/deletion of a large part of the sequence
Some of these changes are harmless (benign) while others can cause disease and are called mutations.
Most mutations are inherited from one or both parents. However, sometimes a mutation can arise spontaneously (de novo) or due to exposure to external factors in developing embryo or fetus.
Mutations in a gene can change the instructions to make the protein. This can lead to the gene not producing any protein at all; to produce a defective protein that cannot perform its functions in the cell; or to produce a protein that harms other proteins.
It is one of the scenarios above, where the protein is not performing its intended function, that can cause genetic disease. Depending on the function of the missing or abnormal protein, the individual carrying the mutation can be affected in different parts of his/her body and develops the symptoms of the disease.
To date more than 6,000 single gene disorders have been identified. There are also complex genetic diseases which are caused by mutations in more than one gene.
An individual carries two copies of each gene, one inherited from each biological parent. Exceptions are genes in certain regions of the sex chromosome.
Both copies may be healthy, one may be healthy while the other may carry a mutation, or both may carry mutations. If the person carries a mutation in at least one of their gene copies, then they can pass on that mutation to their offspring.
In this manner, genetic mutations can be inherited and passed down from generation to generation.
Not always. This depends on the gene with the mutation.
For some genes, both copies of the gene (the one inherited from the mother and the one inherited from the father) should have a mutation causing both copies of the gene to be non-working. So if the individual inherits one mutated copy of the gene but the second copy is working, they do have disease. However, they are a carrier for a mutation and can pass on the mutation to the next generation. Diseases inherited in this manner are referred to as autosomal recessive diseases.
For some genes, a mutation when present in only one of the two gene copies can cause disease in the individual. Having a normal second copy does not offer any protection for these diseases. So if an individual inherits a mutation from a parent who is affected, then the individual is also likely to be affected themselves. Diseases inherited in this manner are referred to as autosomal dominant diseases.
When the mutation is present in a gene located in certain regions of the X chromosome, men are more frequently affected than women. This is because unlike the other 22 pairs of chromosomes, sex chromosomes in men are not completely paired. Men have one X chromosome and one Y chromosome and some of the genes have a copy of both chromosomes. When men inherit a mutation in a gene that is only present in their X chromosome without a copy of the Y chromosome, their only copy of this gene is non-working. Therefore, they are affected with the disease. Women, on the other hand, have two X chromosomes. That means they have a high chance of being protected by a second working copy of the gene. Diseases inherited in this manner are called X-linked diseases.
Mitochondria are little energy factories inside each cell that make energy for the body.
Apart from the DNA in the nucleus of each of our cells, there is also DNA present in the mitochondria. However, mtDNA is inherited only from the mother. That means if the mother’s mtDNA carries a mutation, she will pass it on to her children and, depending on the amount of mitochondria with the mutation, the children can be affected with mitochondrial disease.
It is possible to analyze an individual’s DNA to determine whether there are disease-causing mutations present. This analysis is called genetic testing. Depending on the type of mutation that is to be detected, the testing technique may vary. Sequencing is one of the most common techniques – it involves reading the DNA sequence letter by letter. This can reveal mutations like an insertion, deletion or a replacement of a DNA segment.
Other techniques exist to test for larger insertions and deletions, and missing chromosomes. Another way to do genetic testing is by analyzing the products of these genes, i.e. proteins. For example, if an abnormal amount of a particular protein is produced, it could be because the gene associated with that protein is faulty.
Since DNA is present in almost all cells of the body, there are multiple ways of collecting a sample for genetic testing. It could be a sample of blood or other body fluids or tissues.
Genetic tests can be performed on unborn fetuses during pregnancy using samples from amniotic fluid, chorionic villi or fetal blood.
- Genetic testing is the best and often only way to make an accurate and speedy diagnosis of rare genetic diseases.
- Genetic testing can reveal if you carry mutations that predisposes you to different genetic diseases.
- Genetic testing can predict the likelihood of you passing on a mutation to your children.
- If you have a genetic disease or carry a disease-causing mutation, other family members can then be tested. If they are aware of the risk, they can plan their lives better and obtain the support they need.
- If you have a family history of genetic disease and are planning to have children, it could be useful to conduct genetic tests before your child is born (before or during pregnancy).
- It makes further investigations to confirm the diagnosis unnecessary, which is beneficial for the patient and the healthcare system.
- A definite diagnosis can be a great relief to patients and families, especially if they have been searching for the answer for a long time.
- It can guide the physician in choosing the most suitable therapy and support for the patient.
- The results of genetic testing may be useful for future family planning, adopting preventive healthcare measures and to help other family members understand their risks.
You might want to discuss this with your physician or with our experts, especially if you fall into one or more of these categories:
- Those who have symptoms of a genetic disease and want to get it diagnosed
- Those who have a family history of a specific genetic disease and want to predict their susceptibility even if they have no symptoms at the moment
- Those who belong to an ethnic group that is prone to a specific genetic disease
- Those who carry a mutation but are not affected themselves, although there is a risk of their children being affected
- Genetic testing is most reliable for monogenic disorders. These are those diseases that are caused primarily by a mutation(s) in a single gene. We know of about 6,000 single gene diseases today and CENTOGENE tests for all of them.
- Genetic testing can also be used to detect somatic mutations. These mutations do not exist in all cells of the body, only in some of the cells. These cannot be passed from one generation to another. This type of testing is performed on cancer tumors to help guide treatment. CENTOGENE offers somatic testing for tumor samples.
- Genetic testing for other common diseases, caused by a combination of genetic and environmental factors such as heart attacks, diabetes, high blood pressure, etc., is more challenging. Reliable data to support such testing for these diseases is currently not available and testing is still in development.
Your physician should send us a request for a specific genetic test based on your clinical symptoms. We also need the clinical symptoms to be sent to us to help with the analysis of the test results. If your physician needs assistance in choosing the right genetic test for you, CENTOGENE can help him/her decide on the best testing method.
Once the sample is processed, CENTOGENE uses its software to analyze the data, detect any changes in your DNA and interpret if this is a disease-causing mutation or not.
- Hotspot testing – For detecting a few known common disease-causing mutations in certain genes
- Full gene sequencing – For detecting any mutation which can be present within an entire gene
- Deletion/duplication testing – To detect large stretches of missing or extra regions within a gene
- Next generation sequencing (NGS) panels – To detect mutations in multiple genes related to a specific symptom or disease at the same time
- Whole exome sequencing (WES) – To analyze all 20,000 genes at once to identify causative mutations in complex patients
- Whole genome sequencing (WGS) – To detect mutations in the complete genome, i.e. including genes and the regions of the DNA which do not have genes at the same time
Normally, cells in our body grow and divide in a strictly regulated manner. These strict conditions are coded in the genes. Mutations in genes which control this regulated growth cycle can disrupt this process and cause cells to grow in an uncontrolled manner. When this happens a tumor is formed and it is termed as cancer.
Some cells in a tumor develop the ability to break off and spread to other parts of the body to form new tumors. This is called metastasis of the cancer.
Some mutations, called germline mutations, are present from birth. If these mutations are present in genes that control cell growth and development and cell repair, they can lead to the development of cancer. Such cancers occur at an earlier age and can affect different organs. Also, the mutation can be passed down from one generation to the next. An example of this is the hereditary breast and ovarian cancer syndrome which is caused by inherited mutations in the BRCA1 and BRCA2 genes.
However, most cancers involve the sudden introduction of mutations in one cell during its lifetime. These mutations, called somatic mutations, happen randomly during cell division, or due to exposure to harmful environmental agents, such as radiation or chemicals. If enough such mutations build up inside a cell, it can turn cancerous due to the loss of control of growth and development.
We already know some genes in which mutations when inherited can cause specific cancers. Genetic testing can detect these mutations and help individuals take preventive measures to lower their risk of developing the cancer.
Additionally, every tumor has its own characteristic somatic mutation profile. So tumor cells can be tested for somatic mutations and depending on the results, it is possible to determine the best therapy and, to make a more accurate prognosis. Testing for these somatic mutations may also help in determining the success of a specific therapy.
However, please note that even with genetic testing it is not always possible to detect the cancer early in all individuals at risk, including an individual with a known predisposition.
The choice is a personal one. Make sure you agree to the test only if you understand why you need it and are confident that you want and can handle this information.
Do not be pressured by relatives, healthcare providers or anyone else. Remember that every person is free to decide whether they want a genetic test or not, and also whether to be informed about the results of the test or not.
Make sure you ask any questions you have and voice all your concerns before you make a decision. Genetic counseling is one way to ensure that you have all the information required to help you make this decision.
Some questions you may want to ask your physician are on What to ask your doctor.
Taking a genetic test, waiting for the results, and then receiving them may cause a range of mixed emotions such as stress, anxiety, relief or guilt. The emotional consequences of genetic testing must be considered irrespective of whether the results are good, bad or inconclusive.
This is why genetic counseling is strongly recommended to people considering genetic tested.
Due to the possible serious impact of genetic testing, you are strongly advised to seek genetic counseling before, during and after a genetic test. A specially trained professional called a genetic counselor will provide you and your family with all the information and advice needed.
The counselor will inform you about the consequences and the nature of the disorder, the probability of developing or transmitting it, and the options available for disease management and family planning. This is all done taking into account your situation and needs. The counselor will help you in making a decision on whether to have the genetic test or not.
Genetic counseling is recommended both before and after the test. Before testing, the counselors try to make sure that you are psychologically prepared to cope with the test results, and that you have enough balanced information to be able to provide a truly informed consent to proceed with testing.
After testing, genetic counselors will explain the test results and help you and your family adjust to the results. They can help you arrange whatever prevention and screening measures are appropriate and necessary in the future.
Sometimes a genetic change is detected in a person’s DNA but there is not enough information available to tell if it is disease-causing or not. An inconclusive result cannot confirm or rule out a specific diagnosis or indicate whether a person has an increased risk of developing a disorder. In some cases, testing other affected and unaffected family members can help clarify this type of result and should be discussed in detail with your physician.
Also, advances in this field of science and more powerful technologies are providing us with more and more information every day. CENTOGENE’s databases are constantly updated with new findings that emerge in the literature, allowing us to reduce the number of such inconclusive findings.
Not necessarily. Usually, a positive test is not a 100% guarantee that a person will develop the disease.
Depending on the gene, two people with exactly the same mutation in the same gene may have different outcomes. One may develop the disease while the other person may remain healthy or might develop a less severe form of the disease. Your genetic background may play a role in the disease, but in some cases, other yet unknown factors may also be influencing whether or not you develop symptoms.
Again, there is no guarantee. A negative test might indicate that you or your family member is not affected by a particular disorder, not a carrier of a specific genetic condition or does not have an increased risk of developing a certain disease.
However, further testing may be required to confirm a negative result. A single test cannot always detect all possible genetic changes that cause a particular genetic condition.
With few exceptions, most genetic diseases cannot be cured. For certain genetic diseases, therapy options are starting to emerge and are now available but these are rare and can also be expensive.
However, depending on what the disease is, better options to manage the disease are emerging with new findings being made. A genetic diagnosis of a specific disease will enable the identification of the best options for you.
We are comprehensive: CENTOGENE offers the highest number of single gene tests and multigene tests.
We can detect novel mutations: CENTOGENE offers whole exome sequencing and whole genome sequencing combined with advanced end-to-end bioinformatic analysis, ideal for finding novel mutations and identifying atypical presentations of a disease.
We are up-to-date: CENTOGENE is continually being updated with new findings and developments in the field of genetics and translating these into products and services.
Our reports are clear: CENTOGENE’s reports explain the scope of the test, offer interpretations of results and give medical advice.
We are fast: CENTOGENE offers the most attractive turnaround times for genetic testing.
We are convenient: CENTOGENE requires only minimal amounts of patient samples for a genetic test; in most cases only a few spots of dried blood or saliva samples are needed.
Our experts are here for you: The quality of our services is guaranteed by our experienced team of experts in the fields of genetics and medicine, molecular biology, biochemistry, bioinformatics and information technology. Your physician can consult with them without any additional costs before, during and after testing.
Our results are accurate: Our methods and technologies have a sensitivity and specificity close to 100%; our mutation detection rate is among the highest of all academic and nonacademic institutions.
Our results are crosschecked: A team of highly qualified and experienced scientists and clinicians make sure the test result data are valid and interpreted correctly.
Quality is assured: Our tests are designed with the highest standards and in accordance with the latest guidelines for genetic testing.
Our labs are state-of-the-art: All tests are carried out in our accredited and internationally certified laboratory.
Your data is safe: CENTOGENE guarantees privacy and security. All samples are encoded and documented in accordance with international regulations.