GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2007-10 > 1191863456


From: Jim T <>
Subject: Re: [DNA] Why chromosomes?
Date: Mon, 8 Oct 2007 10:10:56 -0700 (PDT)
In-Reply-To: <mailman.52134.1191804003.9735.genealogy-dna@rootsweb.com>


From: Gary Merrill <>
>> Somewhere in the very distant past, we had an ancestor with
one
>> chromosome. At some point, that chromosome was duplicated,
and
>> we had an ancestor with two chromosomes. Organisms with two
>> chromosomes were able to evolve faster, and out competed
>> organisms with one chromosome.
>
> Not only in the very distant past, but (happily) every day
> since then.
>
> Some basic high school biology.
>
> Diploid organisms like higher plants and animals have two
> sets of chromosomes as a result of sexual reproduction.
> Before sexual reproduction, mutation was the only mechanism
> of evolutionary change.
<snip>

You are quite right. I made a mistake when I wrote this
passage; I left out the word "pairs". I meant to write about
the first organism with two pairs of chromosomes, rather than
two chromosomes, i.e., we had a distant ancestor with one pair
of chromosomes, and that pair of chromosomes was duplicated to
give an organism with two pairs of chromosomes.

Jim Turner



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