dna

[sudu]

is there any possibilty that by some freak of nature two people (completely non related) will end up having the exact same set of DNA?

[dynamicduo]

Yes, it is possible but so unlikely as to be negligable to all intents.

What is the chance of two people completely independently writing a massive novel and coming up with exactly the same words in exactly the same order?

A similar idea - theoretically possible but pretty unlikely!

[rojash]

Actually, it's much more likely than dynamicduo's example, because the rules for constructing a novel are much looser than those for DNA.

[dynamicduo]

not sure what rojash's answer is saying is more likely.

I don't know too much about writing novels but given that the human genome contains around 3 million base pairs and that each base pair has 4 possibilities (A, T, G or C) that gives 4 to the power of 3 billion possibilities. Therfore not good odds to put your money on getting two unrelated humans to have the same sequence of DNA

OK, before anyone criticises, I know that a lot of DNA is 'fixed' so that the organism is a human!!

[rojash]

What I'm saying duo is roughly: "How many ways can a novelist indicate that someone walked into a room?" -squillions. "How many ways can DNA indicate (say) the color of someone's eyes?" - not many. As you say, a lot of DNA is fixed. The remainder conforms to very strict rules about what can occur where in the chain. So it's much more likely that you could have two independently produced but almost identical strains of DNA, than that you could have two almost identical (i.e. word for word) novels, even if the overall stories were the same.

[Peter Pedant]

oh, I see what you mean.

I think that there are a billion bp in the human genome, 90% is needed to run a cell and so will be identical.

dogs and wolves share 99.9%, so you could say if you differ by more than 0.1% then you arent human.

so that means around a million differences, ut that does not mean a one-in-a million chance., you will have to multiply p1 times p2 times p3 intil you get to p,one million.

so even if each p is 1 in 4 - four base pairs - it is still one in 4 to the power of a million

hmm squillions...

[rojash]

Squillion, see below:

http://thesaurus.maths.org/mmkb/entry.html?action=****** ***&id=1385