# [ExI] digital resurrection of a genome

Fri Jul 3 04:15:51 UTC 2015

```On Thu, Jul 2, 2015 at 7:56 PM, spike <spike66 at att.net> wrote:

> *From:* extropy-chat [mailto:extropy-chat-bounces at lists.extropy.org] *On
> *Sent:* Thursday, July 02, 2015 7:14 PM
> *To:* ExI chat list
> *Subject:* Re: [ExI] digital resurrection of a genome
>
>
>
> >…What happens if any of the guy's genes did not make it into anyone
> still alive at the time of comparison?  (Most simply, one gene happening in
> all 25 cases to not make it into the fertilizing sperm.)
>
>
>
> I don’t know Adrian.  Do we have any hipsters in that area?
>
>
>
> Are there any computer sims we might reference?  I should know this, but I
> don’t.  Oh the shame, the ignominy is nearly more than I can bear.
>

Simple math, actually.  The probability of a given gene of a father getting
into a specific sperm of that father is roughly 50%.  (Genes come in pairs;
sperm contain one from each of these pairs.)  There are 25 specific sperm
that lead to those 25 specific children.  So the odds are about 1/2^25 for
any given gene.  (1 - 1/2^25)^x, where x is the number of genes in the
human genome (last estimate I heard was around 20,000), is the odds that
each one of the genes made it into at least one direct descendant.
(Assuming 20K genes, I calculate that's between 99.9% and 99.99% likely.)

However, that is simply the odds for the 25 children.  Similar math,
combined with a family tree showing how many generations from common
ancestor to all living (and identified) descendants, can factor in the
possibility that at least one gene was bred out in the intervening
generations.  (This ignores the chance of mutation, though it's few enough
generations that this likely won't significantly affect the results.)

And even if you collectively do have all of them, how do you know for sure
which ones were his?  One that all of you share could have been shared by
his wives and mistresses (perhaps he favored a certain quality of hair or
fingers) but not by him.
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