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Archiver > GENEALOGY-DNA > 2008-04 > 1208097572

From: "Ken Nordtvedt" <>
Subject: Re: [DNA] underestimating variance
Date: Sun, 13 Apr 2008 08:39:32 -0600
References: <40037.65124.qm@web28303.mail.ukl.yahoo.com><007d01c8997b\$2a314bc0\$6400a8c0@Ken1><000001c89d57\$56159630\$0201a8c0@owner8151f88a9><008b01c89d6f\$4e1ccc60\$6400a8c0@Ken1>

----- Original Message -----
From: "Ken Nordtvedt" <>
>
> ----- Original Message -----
> From: "Sandy Paterson" <>
> To: <>
> Sent: Sunday, April 13, 2008 5:12 AM
> Subject: Re: [DNA] underestimating variance

>> Here's an example, using a mutation rate of .002 and 1000 generations.
>>
>> +7 .0000
>> +6 .0002
>> +5 .0013
>> +4 .0069
>> +3 .0288
>> +2 .0933
>> +1 .2153
>> +0 .3084
>> -1 .2153
>> -2 .0933
>> -3 .0288
>> -4 .0069
>> -5 .0013
>> -6 .0002
>> -7 .0000
>>
>> 1.0000
>>
>> So .3084 should be modal, .2153 should be modal +-1, and so on.
>>
>> Sandy Paterson

This distribution is good for a single line of descendants; after 1000
generations there would be a 30.8 percent chance of still being modal, 21.5
percent chance each for being +1 or -1 from modal, etc.

It can not give you the distribution for a whole population of descendants,
because those descendants may reproduce differently. Suppose sometime after
the founder one of his descendants at +1 migrated over into Paradise Valley
which was fertile and empty. His descendants were very numerous; that
valley's population grew for some time at a faster rate than the parent
population --- the classical story of life filling new niches. The
resulting population distribution for this marker would be asymmetric and
best considered as the original distribution you show above plus another
younger distribution centered on +1. In fact this is how I get my first
clues about bimodality of a distribution when I look at a database
distribution for markers. Ken

Ken

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