Looking only at genetic code, is it possible that there have ever been two genetically identical people who are not twins (or clones)? How many medically distinct human beings can their actually be?
I’m assuming that we’re only talking about biologically modern human beings. So the genes that make us human cannot be eligible for variation.
If we don’t include environmental factors and non-DNA genetic material, what is the actual number of genes that can vary from one person to another? Do we even understand the human genome well enough to make this kind of calculation?
I’m assuming from combinatorial math that it’s more humans than can ever exist through the course of the entire universe. But what is the actual number? If those genes are varied at random, how many people will it take before they say a 50% chance that two of them are identical? For example, it only takes 23 people to have a 50% chance that at least two of them have the same birthday.
Edit: I found an interesting article about the complications with trying to calculate this number. The number seems to be on the order of 10^(tens or hundreds of thousands)
My gf works in human remains identification. On the bottom of the DNA identification reports, they have a certainty estimate:
1 in 19,000,000,000,000 (trillion) chance of being incorrect.
So if that’s any estimate of how many variations there can be, I’d say chances of repeats are pretty low lol
Note: I didn’t believe her when she quoted 1 in 13 trillion, so she double checked the next day. They seem… confident
Correction: I talked to her again, and was completely wrong, because my memory refused to accept the real number:
1 in 200,000,000,000,000 (trillion) chance of being wrong.
And to the commenter that commented about common identifiers, you are correct. She’s fairly confident they use the SNP method.
I hope people reading this have SOME measure in their mind of how immeasurable even ONE trillion really is.
To count to a million it takes about 11.5 days, a billion roughly 31.7 years, and a trillion approximately 31,700 years, assuming one number per second without breaks. Then do it 18 more times.
Literally mind boggling. I made a correction and was wrong by a factor of 10 because I couldn’t accept it was that high. But she showed me a screenshot of the report…
Does have me wondering what the ratio looks like when applied to isolated (maybe mildly inbred) communities.
As in, there’s a lot of genetic variety for humans as a whole, but maybe less so for communities that, uhh, don’t get out much.
That’s pretty interesting. I’ve done some genotyping before, and I’m guessing that they probably check a handful of distinctive genes, not the entire genome.
For example, if they checked 45 binary markers (e.g. positive or negative) that would get you into that ballpark (assuming that they are evenly distributed and not correlated). Of course, there are also markers that are not binary but can have many different variations other than positive and negative.
That’s actually really cool to know. She was fairly confident they use the SNP method (it’s a third party provider), and described it the way you did. Sounds like full genome is possible but she didn’t think it likely, your explanation would support that.
Also, I made a correction to the numbers…I was very wrong lol