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From: dd@beta.UUCP
Newsgroups: sci.bio
Subject: Re: Dumb Questions about Mitochondria
Message-ID: <8996@beta.UUCP>
Date: Sat, 15-Aug-87 17:16:15 EDT
Article-I.D.: beta.8996
Posted: Sat Aug 15 17:16:15 1987
Date-Received: Sun, 16-Aug-87 10:07:48 EDT
References: <52@citcom.UUCP>
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 26
Summary: own DNA:yes always from mom: no

In article <52@citcom.UUCP>, jack@citcom.UUCP (Jack Waugh) writes:
> Which species have mitochondria?
Anything with a nucleus that wants to live off of oxygen. 
 
> Do mitochondria always have their own DNA and hence
> genetic line independent of nuclear DNA?
It varies by kingdom.  Plants have relatively large >150KB mito genomes;
mammaliam mitochondria have 16 KB or so genomes.  The difference is that
more of the proteins required for the mitochrondria are encoded in the
mammalian case.  There was an interesting article in Science in 1984 by
Lewin that discussed gene migration from the mitochondrial genome to the host.
The proteins that remain encoded in the mammalian mt genome are very hydro-
phobic and do not cross membranes well.

Also remember that mt are descended from procaryotes, and there are at least
two separate lines of descent (plants vs. everything else).

> In sexually reproducing species, do the mitochondrial
> genes always come from the mother (I understand that
> this is the case for humans).
In some fungi the mt genomes fuse when the zygote is formed and the 
mt inherited by the daughter cells is therefore recombinant.  In mammals the
mt come from the egg, and only very, very rarely does the mt from the sperm
make it into the zygote.

dan davison/theoretical biology/t-10 ms K710/los alamos national lab/NM 87545