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This is not accurate. Coarsely, there are roughly 3 million SNPs (out of 3 billion total haploid bases) per individual. When we talk about individuals "sharing"
by adenadel 8y ago
This is not accurate. Coarsely, there are roughly 3 million SNPs (out of 3 billion total haploid bases) per individual. When we talk about individuals "sharing" DNA we mean these variants and not the 99.X% of DNA that we all have in common. When we refer to random mutations in the germline (i.e. de novo variants) current estimates of de novo variants per individual are in the low hundreds.
The other factors you discuss are more likely to cause issues. One major one is the error rate of the microarray because of the high number of genotypes being assayed. If the chip has an error rate of 0.1% and 500k tests are performed you would expect 500 mis-calls. I used to work for Illumina, who makes these chips, but I worked on the DNA sequencing side of things so I don't know the actual error rate off the top of my head.
- klmr 8y agoRight, de novo mutation rate is much lower (even lower than what you wrote, just slightly above 1e-8 according to deCODE). The 1/1000 rate is the average difference between two random individuals (not twins), which corresponds to your 3M SNPs per 3B bases.
- adenadel 8y agoYes, but you referred to them as random mutations, which is not the case. They are inherited variants. The DNA replication error rate is nowhere near 1 in 1000.
- klmr 8y agoHence my correction. Without looking it up now, the actual replication error rate is probably close to the deCODE rate for de novo mutations (modulo gamete selection, so probably higher than that).