Of the approximately 19,000 human genes, about how many have one allele that occurs with appreciable frequency in the current human population, how many have two alleles, and so on? (By "appreciable frequency", I mean, say, is found in at least 1% of the population, which seems to be the rule of thumb for classifying a gene as polymorphic in the population.)

I'm not looking for an exact breakdown for every single number of allele variants - I'm just curious, does the typical human gene have only one (frequently found) allele? Or two, as is often implied in elementary genetics texts? Or five, or 10, or 100? What does the approximate distribution look like?

According to the Wikipedia article linked above, the most polymorphic genes known are those coding for the Major Histocompatibility Complex (MHC), with the HLA-B HLA-DRB1 loci having 200 significant alleles, so I guess 200 is the upper end of the spectrum. (Although I don't know whether "the HLA-B HLA-DRB1 loci" refers to a single gene or several, so maybe 200 alleles is higher than any single gene has.)

  • $\begingroup$ Also, when Wikipedia says that the MHC genes are "the most polymorphic genes known", do they mean the most polymorphic human genes, or the most polymotphic genes across all species? I would assume that e.g. bacteria display a much higher level of gene polymorphism than humans, because they have a much higher rate of mutations per base pair. $\endgroup$ – tparker Jan 5 '19 at 20:49
  • $\begingroup$ Ah, I might have misunderstood what you are after. Are you interested in 1) the distribution of the number of alleles per locus or in 2) the distribution of frequencies per allele. The second one is the SFS. You can totally consider a SFS for loci that have more than one allele. Although, most often SFS are drawn from SNP data, as such there is rarely more than two alleles at a given SNP. $\endgroup$ – Remi.b Jan 5 '19 at 21:07
  • $\begingroup$ @Remi.b I'm after distribution (1). $\endgroup$ – tparker Jan 5 '19 at 21:18
  • $\begingroup$ Ok, I've removed most of my comments, then! $\endgroup$ – Remi.b Jan 5 '19 at 23:00

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