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Archiver > GENEALOGY-DNA > 2011-02 > 1297526797


From: "Diana Gale Matthiesen" <>
Subject: Re: [DNA] GENEALOGY-DNA Digest, Vol 6, Issue 141
Date: Sat, 12 Feb 2011 11:06:37 -0500
References: <mailman.20291.1297369649.2081.genealogy-dna@rootsweb.com> <20110210161010.N3LGH.1170777.imail@fed1rmwml31> <AANLkTimZ_Xp6x_PDr820XL4RMWgJ3tS2Nc=xJDgqjD_X@mail.gmail.com> <000f01cbca9e$1dcae1f0$5960a5d0$@dgmweb.net><8CFC9625-CFE0-4AD8-9105-39231E636EA4@vizachero.com>
In-Reply-To: <8CFC9625-CFE0-4AD8-9105-39231E636EA4@vizachero.com>


> > On Feb 12, 2011, at 5:17 AM, Diana Gale Matthiesen wrote:
> > I agree that in the "traditional" definition of
> > "chromosome" -- the ancient one I was taught in
> > school -- mitochondrial DNA would not be
> > considered a chromosome, but I'm afraid that
> > meaning appears to have changed...
>
> From: Vincent Vizachero
> Sent: Saturday, February 12, 2011 7:16 AM
>
> Paul is correct. I don't think any biologist would
> call a mitochondrion a "chromosome" (not when they
> were worried about being correct, at least).

Neither of the messages Paul was responding to (from Richard who was
responding to Charles) used the word, "mitochondria," or, in any
sense, appeared to be referring to the organelle. Richard's message
used the phrase, "mitochondrial DNA," so I assumed Paul merely
misspoke when he used the lone word, "mitochondria," so went with what
I thought he meant: mitochondrial DNA. No one had mentioned the
organelle, so I didn't see how he could have been referring to the
organelle. I actually do try to read people's messages in context, so
I understand what they are trying to say, instead of parsing every
word out of context and equivocating for the sole purpose of
disagreeing.

If Paul meant what I thought he did (viz., mitochondrial DNA, not
mitochondria), then in principle I agree with him, and I said so. But
I think the point has been reached where we cannot correct someone for
calling mtDNA a "chromosome," which is what it appeared to me his was
doing in responding to Richard, because so many people are doing it,
for example:

http://dienekes.blogspot.com/2009/01/y-chromosomes-and-mtdna-of-korean
s.html

http://www.biol.sc.edu/faculty/duggins.html

http://www.pcdunham.net/TestProject.htm

> The Wikipedia article Diana cited does not actually support her
> contradiction of Paul.

The Wikipedia article:
http://en.wikipedia.org/wiki/Chromosome
says, in the second paragraph, last sentence: "Furthermore, cells may
contain more than one type of chromosome; for example, mitochondria in
most eukaryotes and chloroplasts in plants have their own small
chromosomes."

It does seem pretty clear they are referring to mtDNA as being in the
form of "chromosomes."

> And the Wikipedia article on mitochondria
> contains this: "A mitochondrion contains
> DNA, which is organized as several copies
> of a single, circular chromosome."
>
> In other words, the mitochondria contain
> chromosomes. They are not, themselves,
> chromosomes.

No dispute here, this is Bio 101. The organelle is not the DNA, it
contains the DNA. I would be inclined, though, to dispute that the
circular "genophore" of mitochondrial DNA is a proper "chromosome."
Please see:

http://en.wikipedia.org/wiki/Genophore

where it says, "A genophore is the DNA of a prokaryote. This is
commonly referred to as a prokaryotic chromosome. The term chromosome
is misleading for a genophore because the genophore lacks chromatin...
Many eukaryotes (such as plants and animals) carry genophores in
organelles such as mitochondria and chloroplasts."

But it appears the definition of what constitutes a chromosome has
broadened/relaxed/eroded, so I have to accept the change. I will
probably not use the word that way, myself, but I'm not going to
correct someone else for doing so.

Diana




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