Kira Peikoff sent a sample of her DNA to three different companies — including 23andMe — each of which reported wildly differing results for several very good reasons, including the limited sample size:
The genetic testing that these three companies offer is premised on reading segments of DNA called SNPs (pronounced snips), for single nucleotide polymorphisms. But these segments, which have been linked to diseases in research studies, vary among people.
Scientists have identified about 10 million SNPs within our three billion nucleotides. But an entire genome sequencing — looking at all three billion nucleotides — would cost around $3,000; the tests I took examined fewer than a million SNPs.
The results of these DNA testing companies appear to be approximately as reliable as that of an Ouija board, or perhaps some tea leaves. The biggest difference is that they claim scientific accuracy and reliability, but possess neither trait.