Timeline for Why do almost all SNPs have two alleles?
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4 events
| when toggle format | what | by | license | comment | |
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| Aug 20, 2015 at 22:46 | vote | accept | Paul | ||
| Aug 20, 2015 at 22:17 | comment | added | Athe | The percentage varies between definitions of polymorphisms, some say 1%, some say 5%, but you got the idea. You have to think that is not a loci, but rather a single position of a loci. Even if all locis accumulated 1 single base mutation each generation with a 2.5 kb length (that is the average loci if i remember correctly) it would still be 1/2500 probability of affecting the aame letter and times 2/3 (as one of the mutations would be a reversion to the original). So yeah, it is highly improbable. | |
| Aug 20, 2015 at 21:38 | comment | added | Paul | To be sure I understand, the idea is that say 100% of a population has an "A" at some loci at some point in time. Then say a mutation causes a member, call her Alice, of the population to have the loci at that base replaced with a "C", and they pass that mutation on to their offspring. After some time, that loci would be considered a SNP if enough of Alice's descendants survived such that they make up 1% of the population. The only way for another allele to exist is is if someone else at some other point in time ALSO has a mutation at that loci that switches away from "A" or "C", which is rare | |
| Aug 20, 2015 at 21:21 | history | answered | Athe | CC BY-SA 3.0 |