For such a powerful product, the 23andMe® Personal Genetic Service process is fairly simple: order, spit, see your data. But between you putting your sample in the mail and us alerting you that your data is ready, there's actually quite a bit that goes on at the laboratory. Labcorp, our third party laboratory located in the U.S., takes multiple steps to process your sample, which are described in the article and short video below.
Step 1: The Visual Exam
Samples arrive at the lab every day. After opening each sample box, the technicians visually inspect each sample to make sure that the sample is acceptable for testing. For example, making sure that a sample contains fluid up to the "fill line" on the side of the tube. Occasionally a sample will not pass this step. This can be due to reasons including, but not limited to, the kit leaking while in transit or because the preservative solution wasn't released into the tube when the customer snapped the oblong cap onto the collection funnel. If a sample tube doesn't contain enough liquid we immediately notify the individual that registered the kit via email and offer a replacement kit within their account so they can spit again.
Once a sample passes the visual inspection, the barcode on the sample is scanned and the sample is prepared for the next step of laboratory processing; for privacy reasons, the barcode is the only identifying information the laboratory has.
Step 2: DNA Extraction
If a sample passes the visual inspection, it moves on to the next steps of laboratory processing, DNA extraction. DNA extraction is the process the laboratory uses to isolate and purify the DNA in your saliva. Once the DNA is extracted from the saliva sample, the concentration is measured to make sure there is enough DNA needed to process on the genotyping chip.
If the first attempt at DNA extraction does not yield satisfactory results, a second attempt is made with some saliva that was set aside before the process was started. If this second try fails, we contact the customer and send a free replacement kit so he or she can spit again. The hope is that this second sample will be DNA-rich and ready to go!
The most common cause of low DNA is that the preservative solution is not fully released into the tube. But some people just naturally have low DNA in their saliva. If a customer is sent a replacement kit, and two tries on the new saliva sample still don't yield enough DNA, then unfortunately the customer probably won't be able to use our service and a refund for the kit fee minus shipping and handling is provided. Luckily, this is a very rare occurrence.
Step 3: Genotyping
Samples that yield sufficient quantities of DNA are genotyped on our custom SNP chip (or microarray). This process is performed in batches of approximately 96 samples. We monitor the process to make sure it is going as expected. For example, data returned from the genotyping step is quality reviewed to ensure that it meets our standards for call rate and accuracy. If a particular sample fails to give information for at least 98.0% of the markers we test for, we go back to the saliva sample that was set aside in the extraction step and try again.
If a second attempt at genotyping fails, we ship a free replacement kit to the customer so he or she can spit again.
Step 4: Data Return
Once a sample is successfully genotyped, the laboratory sends the resulting data to 23andMe along with the barcode that came with the sample. This allows us to return the information to the proper account and begin interpreting your data.