F.A.Qs

There are 3 major categories for identifying genetic variations: a) PCR ("polymerase chain reaction") in which, in one tube, one can identify up to three different genetic variations (hereinafter referred to as "multiplexing"); b. "Micro-array" platforms, which essentially represent multiple PCR reactions on a chip, or independent DNA synthesis reactions (technology allowing miniaturization of these chemical reactions); c) Sequencing methods, in which 200-400 nucleotide long DNA chains are sequenced based on the base in turn. One of the major differences between methods a) and b) and c) sequencing, respectively, is that the sequencing method allows much more iterations (repeats) of the DNA sequence identification reaction, compared to the PCR and micro- array. Why is this important for a genetic (or nutrigenetic) test? The more numerous these iterations (that is replications of the same chemical reaction to identify genetic variations), the more robust the results are. Generally, genetic variation identification (genotyping) reactions, regardless of the method used, have a probability of success of 85-90%. In other words, running a single genotyping reaction will yield 85-90% true results. This means that because the probability of failure (false positive or false negative results) is close to 0%, the same genotyping reaction must be run several times. For example, the success rate of 100 responses will be 85. For 85 times the same result was generated, while false results were generated in only 15 responses. In contrast, if a single genotyping reaction is run, the chances of failure are 1 in 6. This means that if I test six people using a single reaction to each, a 6th individual will generate a false result. This limitation is inevitable, and comes from how chemical reactions take place - never with 100% accuracy. In practice, this limitation is solved by repeating the reaction several times, until the probability of repeating the error approaches 0% and becomes negligible. Due to the costs involved, the PCR method generally uses 3 replicates (3 iterations), ie the reaction is run separately 3 times. Under these conditions, the probability that the error will repeat 3 times in a row (ie genotyping to produce an erroneous and unidentified result as such) is: 0.15 x 0.15 x 0.15 = 0.34%. This means that out of 1,000 people tested, erroneous results (unidentified as such) will exist for 3.4 people. In the case of micro-array methods, there are several iterations (generally less than 10), allowing even greater error reduction. In the case of sequencing, the probability of error is reduced even more, since it is already routine to have a 100-1000x depth of sequencing (ie 100-1000 iterations), which has made the sequencing a standard for genotyping. The Advanced NGx test uses the sequencing method with a depth of at least 100x (mean value).