Archiver > GENEALOGY-DNA > 2010-03 > 1269910486

Subject: Re: [DNA] Family Finder Test
Date: Mon, 29 Mar 2010 18:00:47 -0700
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In-Reply-To: <><><><COL123-DS674F25C03B7B69636B652C8200@phx.gbl><>

I would guess that single crossovers are more common than multiple ones during meiosis I, but I am unaware of any discussion of this in the literature. Undoubtedly, looking at the results within a family with several children would how many crossovers occurred per chromosome per child. It should be possible to gather crossover statistics as more families partake in the FF tests.
Sorry, I knew better when I wrote before that the technical term chiasma is the singular and chiasmata is the plural.

Richard R. Kenyon ("Dick")
.----- Original Message -----
From: John Chandler<mailto:>
To: <mailto:>
Sent: Monday, March 29, 2010 1:07 PM
Subject: Re: [DNA] Family Finder Test

Dick wrote:
> Isn't this assuming a double crossover between an autosome pair?

Yes, for simplicity. The number of crossovers, as I mentioned, is
quite variable.

> I would imply from examples I've seen in genetics texts on
> constructing linkage maps that single crossovers are much more
> likely, i.e. a single chiasmata rather than multiple chiasmata.

Examples in texts are constructed to illustrate concepts, and not
to confuse the reader with unnecessary complication.

Incidentally, the word "chiasmata" is plural!

John Chandler

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