Genetic testing is performed on saliva, blood or tissue samples to analyze genomic DNA, the genetic code each person receives in equal parts from both biological parents at birth.
Although some of the body’s cells may have minor and sporadic changes, overall, the genomic DNA sequence does not change over a lifetime. Thus, the results of a genetic test done at seven years old will be exactly the same as the one done at 90 years old!
What can alter our genetic code?
Minor changes, called “mutations,” can occur over a lifetime in a small number of cells. For example, this can happen due to exposure to radiation or carcinogenic substances (asbestos, certain heavy metals, pollutants, etc.). However, the body’s defence system eliminates most of the cells whose DNA is modified.
If such mutations survive, only the cells that divide from the original affected cell will have the mutated gene, never other cells or tissues. In a limited number of cases, these mutations may give rise to cancer.
Sometimes re-testing is recommended for certain genetic tests, not because the DNA of individuals has changed, but because laboratories have developed new indicators for particular clinical conditions. This may also be the case for pharmacogenetic testing, for example, when clinical practice guidelines suggest using new drug groups.
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