Next-generation sequencing is typically 99.999% accurate at each location of the DNA. Helix has built a state of the art sequencing lab, and they also work closely with Illumina, the market leader in next generation sequencing technologies. Their lab is optimized to provide the highest level of accuracy as they sequence your DNA. Even with all this work, there are some limitations to the technology. In the rare case that Helix is unable to read small portions of your DNA, they will mark that section as "unreadable" rather than guessing. You should feel confident that when you look at your data, it is as accurate as possible.
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