[ExI] Genetic recombination

[spike at rainier66.com]

-----Original Message-----
From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf Of Ben Zaiboc via extropy-chat
...

>>... Do we have those among us who can clarify?  It might be clearer if I had said something like “this series of base pairs was expressed and its origin was from your father, but at this point, it switches over to the next series of base pairs, inherited from your mother.”  I don’t know the best way to express that idea.


>...This might help: 

www.genome.gov/genetics-glossary/Crossing-Over

https://biologynotesonline.com/dna-recombination/

>...The purpose of crossing-over is to get new combinations of alleles, generating diversity. If you had two identical eggs, fertilized by two identical sperm, the result would be astronomically unlikely to produce the same combinations in each...
--
Ben

OK cool thx Ben, that is how I understood it.  It has been a loooong time since I studied it.

In AncestryDNA the DNA kits detect genetic units down to the centiMorgan level.  Imagine we make a simplifying assumption (not a realistic one but a vastly simplifying assumption) that centiMorgans are not divisible (acting as little atoms of DNA kinda) and then treat the chances of crossover as 50% with each centimorgan, then the chances of two recombinations of N alleles being identical is about the same as the chances of two guys flipping a coin N times and getting the same sequence.  If N is 3, the chances of the two fellers getting the same sequence is 2^-3 or one in 8.  Ben does that sound right?

Now again with the (unrealistic) simplifying assumption of treating centimorgans as atoms of DNA, we can estimate (in reality wildly underestimate) the probability that our DNA recombined the way it did.

AncestryDNA has a 50 dollar DNA kit which measures about 7000 centiMorgans.  Recall that experiment I described before where a particular ovum and a particular sperm is recombined a skerjillion times to see if they ever recombine in exactly the same way twice.  With the unrealistic but simplifying assumption of indivisible centimorgans, there are about 2^7000 different ways those two DNA strands can combine.  The hotel guy in Jason's video used the typical number of sperm in a cheerful evening.  He said 200 million, well OK that would need to be a very VERY cheerful evening.  In reality it is probably more like 50 million (but hey, I was a teenager once (I think.))

In any case, if we argue the odds of that cheerful evening producing the comely Nora Alvarez is one is 200 million, this is an unimaginably vast understatement.  As the video comments about the hard game, Nora is not impossible, only absurd.  The chances of that one sperm from the (very)^2 cheerful evening isn't one in 200 million, it's more like one in 10^2300.  Not impossible, absurd.  We are all a product of a one in 10^2300 event.

This is all a sim.  We are all in a simulation.  

Well, OK not we.  You are.  You are the only human.  We are software.  Prove "me" wrong.

spike
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