See below. I'm completely serious. The population prevalence of Tay-Sachs is about 0.4%. (I don't look obviously Ashkenazi - quite the opposite - so there's

See below. I'm completely serious. The population prevalence of Tay-Sachs is about 0.4%. (I don't look obviously Ashkenazi - quite the opposite - so there's little reason to assume I'm in a high-risk population). Therefore, there's a pretty strong prior that we didn't need to worry about it in the first case. Even assuming that the 23andme results have a horrible false negative rate -- let's say they miss 25% of carriers -- a negative result on a single screen (where we know it was actually my data, as Jacques noted) is enough to drive our per-child risk down to about 1 in 4000. The false positive risks are small - follow-up genetic testing using a certified lab is easy. Note that I was creating a deliberately absurdly high number for that false negative rate. The FN rate found, for example, for 23andme's Bloom Syndrome carrier status test is much lower than what I used above. The actual post-test carrier risk when I calculated it was under 1 in 10,000. Perfectly fine for a low-risk situation like ours.