DNA is deoxyribonucleic acid. It is a molecule that is present in nearly all of our cells, responsible for containing all of an individual or living being’s genetic information. This information is unique and unrepeatable in each being, as the combination of elements is constructed in a unique manner. This molecule holds the code that determines an individual’s function and characteristics. This acid also contains the genetic data that will be hereditary; that will transmit what we are to our children, and they to theirs, and so on successively, from generation to generation.
Each DNA molecule is like a very long word. It has the shape of a double helix formed by a combination of four letters (nucleotides); A, T, C and G (adenine, thymine, cytosine and guanine). A simple combination of four letters, of varying length and order, gives rise to something as complex as a living being.
Genes are parts of DNA that contain the information necessary for the production of the proteins that make us up and enable the human body to function.
They are composed of sequences of four different types of nucleotides (A, T, G, C) whose length and order vary from one gene to another. We have an estimated 20,000 genes that code for proteins.
Parents pass their genes on to their children. Every individual has two copies of each of their genes. One comes from their mother, and the other from their father.
The sequence of nucleotides (A, T, G, C) that makes up a gene can have variations:
- One nucleotide may have been replaced by another (a G instead of an A, for example).
- A part of the sequence may have been lost (deletion).
- Other nucleotides may be added to the original gene sequence (insertion).
These variations or alterations in the sequence of a specific gene may be benign and have no consequences. Others may cause disease by generating a dysfunction in the protein they code for. These phenomena are known as mutations, and are the cause of genetic disorders.
They can be caused intrinsically, during physiological DNA replication processes, or by external factors such as radiation.
A child may receive mutations present in their mother and father’s DNA when they inherit it.
These are disorders caused by genetic mutations.
Mutation expression pattern:
Certain diseases are caused by the presence of a single genetic mutation: in other words, just one of the two copies of the gene has a mutation, but it will be enough to produce a dysfunctional protein. This type of disease is known as “autosomal-dominant”.
Other diseases will be developed only if the two copies of the same gene are affected by the same mutation. These are the “autosomal-recessive” diseases. A person can carry a single copy of a mutation, which in this case will be silent, and will not have any repercussion on their health.
If genetic disease is caused by the mutation of a single gene, it is a “monogenic” disease. There may be additional mutations in other genes, but just one can cause a disease.
Other diseases are known as “complex” (they can also be called polygenic or multifactorial) and will depend on the interaction between the individual’s genetics, their lifestyle and/or external risk factors. In such cases, reference can be made to genetic predisposition or susceptibility: certain genetic traits can increase the risk of developing a disease. On another note, certain hygienic habits can modulate this risk, increasing it, or to the contrary, providing a certain protection. External risk factors can play a role in increasing risk.
A typical example is cardiovascular disease. CV disease can be attributed to the sum of individual genetic predisposition and bad lifestyle habits that lead to the development of certain risk factors such as high cholesterol, smoking or hypertension. Someone with predisposition to suffering cardiovascular disease can control/minimize that risk by adopting a cardio-healthy lifestyle (healthy diet, exercise, etc.).
Another example is thrombosis: a person can have a genetic thrombophilic profile, giving them a higher likelihood of developing thrombosis. Personal risk factors such as older age or obesity will increase an individual’s thrombosis risk. External factors such as prolonged immobilization or certain medications can also contribute to increasing that risk. Knowing one’s genetic predisposition facilitates the implementation of prevention measures.
Since parents can pass on their own mutations to their descendants, when faced with a genetic disease it is important to perform a family study to determine whether other members of the family carry the mutation.
Likewise, if a couple wishes to have a child, and one of the parents is affected by a genetic disease, it may be necessary to perform a genetic study to prevent the baby from inheriting the mutation that causes the disease.
There are different types of genetic tests:
- Genetic Diagnostic tests: purpose to identify the presence of one or several genes or mutations to enable a physician to make a more informed clinical decision. The physician can provide a provisional diagnosis based on a number of clinical symptoms, and can gain a comprehensive diagnostic assessment with additional genetic information. These types of test are usually used for monogenic diseases.
- Predictive Genetic tests: provide analysis of an individuals predisposition to developing a disease with a genetic base. These tests are often polygenic and used in more complex diseases in which genetics interact with lifestyle or external risk factors. Software algorithms based on individual genotypes and genetic risk factors are usually used to calculate the overall risk taking both clinical and genetic variables into account.
In the case of predictive genetic tests, an algorithm is a mathematical formula that integrates different elements such as genetic predisposition, and personal and external risk factors. Each element has a “specific weight” that the algorithm considers to calculate a person’s overall risk of developing a disease.
The reliability of the test depends on the level of quality at which the analysis laboratory works (as with any other health exam). In general, they are reliable.
Diagnostic tests are useful enough to confirm a physician’s provisional diagnosis but not to rule out a disease. That limitation is linked to the level of knowledge of the pathology: there may be another causal mutation that has not yet been sufficiently identified at the scientific level.
Predictive tests calculate risks and probabilities. It is important that they be based on strict methodology, with proven results that are recognized at the scientific level. Such tests allow physicians to set prevention measures that are useful and important to care for the patient’s health in the long term.
Both diagnostic and predictive tests are medical tools that require the interpretation of a health care professional, and their intervention to establish a treatment or prevention measures if necessary.
That is why it is important to go to a doctor for them to prescribe the test and discuss the results report together. If you are interested in a genetic test, do not hesitate to contact us.
Contact us for information on physicians in your area you can go to for the test you are interested in.
It’s a very simple process. It can be gathered from a blood or saliva sample. In that case, a special kit is used to gather cells by gentling rubbing the gums with a swab. In other cases, you might be asked to deposit a little saliva in a small container, as with Gen inCode tests.
The saliva sample can be conserved at ambient temperature, and blood in a refrigerated environment.
The physician requesting the genetic test, on your behalf, will receive the report via email. They will then provide you with the report and results during your next appointment, at which time you will be able to discuss the results and any next steps should they be required.
The length of time it will take to return the report to your physician will depend upon the type of test performed and can be between 3 to 10 weeks.
If a monogenic diagnosis is confirmed, your physician will have valuable information to propose the right measures to care for your health. If necessary, your physician can provide guidance on whether other family members should have genetic tests performed.
In the case of a complex disease, the predisposition to develop the pathology may be balanced by adopting prevention measures. Your physician can recommend the modification of certain lifestyle habits. In that case, you can take specific actions to care for your current and future health and prevent or slow down the development of the disease.