How many people does there need to be on earth before one person's DNA matches another?

Answer 1

Well, aside from the obvious answer of identical twins/triplets/clones, etc...

The human genome has 3 billion base pairs. There are 4 possible bases. One way to estimate the probability is to take 4 and raise it to the 3 billionth power. That many people couldn't possibly fit on Earth, and probably not in the whole solar system, either.

This is, of course, inaccurate for several reasons.

1) Not all of the base pair variations will result in a living human being. This would cut the number of base pairs down by 99.99% or more. That much of the genome goes into just making sure you have a brain, ten fingers, etc.

2) Not all possible mutations exist. This would also cut the number of base pairs down, but by an unknown amount.

3) There's been a lot of inbreeding in our history. A Chinese person is going to have a lot more genes in common with another Chinese person. A Jew is going to have a lot more in common with another Jew. For very small populations, say on a small, isolated island, the likelihood of running into the same DNA increases.

All the same, I still think it's so unlikely that two unrelated people will have the same DNA, that I think DNA evidence is still proof beyond a reasonable doubt. (Provided you trust the DNA lab technician.) However, you can bet that there's probably someone out there who looks just like like you, but some differences will still be detectable on the DNA level.

Answer 2

Besides the obvious identical twin factor, there already are enough people. Depending on the rarity/commonality of a person's DNA there are statisticly likely to be 1 in every 2.*** million that a certain DNA would match. Meaning that there could be even 2 othere ppl on Earth now with matching DNA. & hey have you ever heard of ONE person having more than one DNA strand? It's true the discovery health cannel had a special on it a cpl years ago & replays it every so often.....

Answer 3

This is more of a math question. I love these questions lol
anyway the answer is for you to be sure that two people's dna math you need to have 1 more than the possible combinations of dna. Think of it as birthdays, how many people do you need to have to be sure that 2 birthdays math? 367 because then one would be for each day of the year and the extra woul dhave to be repeat one

Answer 4

It cannot ever happen. There are two billion base pairs in the human genome, of which perhaps half are expressed. Changes in the unexpressed genes (introns) have no visible effect, yet will happen for any of the usual reasons (chemical issues, radiation, etc.) So the number of different possible human beings is on the order of 2 to the power of a billion. That number is FAR larger than the total number of particles in the visible universe.

Answer 5

One. It is already technically possible to clone a person. So you would be able to create an exact double!

But seriously; One single human cell comprises of multiple chromosomes (23). Every chromosome consists of billions of molecules, in a specific chain (very complicated). So there must be at least 23 * (a couple of billions)² different DNA strings possible...

Answer 6

The odds that any two (non-twins) people will have identical DNA is for all purposes zero. DNA is so huge and mutates so easily that there's basically no chance for that to happen.

Answer 7

just 2...one normal person and the other can take some DNA from the person and clone him

Answer 8

This I do not know the answer to. However, I do know that that the likelyhood of finding an untaken screen name on Yahoo and AOL is quickly approaching 0.

Answer 9

Regardless of all the data the number is two. Praise the lard.

Answer 10

Great question, I never gave that a thought. Twins would be the only way other than that science could do it I guess, great idea............