Chromosome variation was: RE: "Design up to Scratch?"

From: tpi.hormel@attbi.com
Date: Sat Apr 26 2003 - 18:22:47 EDT

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    Debbie Mann asked:
    > How does evolution change the number of Chromosomes?
    ...

    Well, evolution doesn't change the number of chromosomes. Evolution
    is not the driver of such changes, but it can be the outcome.
    For example, the generation of polyploid plants has been observed
    in labs and this mechanism it is potentially a major factor in some
    forms of plant speciation. I think a few cases in amphibians and
    fish have also been described although it is probably a lot
    rarer in "higher" animals.

    We can also find examples of chromosome splittings as well as
    fusions. Przewalski's horse is an example of the former and humans
    are an example of the latter. Contrary to popular belief, crosses
    between organisms with different numbers of chromosomes don't
    necessarily create sterile progeny (Often, but not always). What
    seems to be important is how well the chromosomal segments can line
    up and segregate during division into gametes.

    A quick search on "polyploidy" and "changes in chromosome numbers"
    pulled this up:

    http://www.madsci.org/posts/archives/may2001/989331026.Ev.r.html

    I also ran across this old post from the defunct evolution
    reflector of the asa:
    http://www.asa3.org/archive/evolution/199505-10/0641.html

    You might recognize some names there...

    - tpi.hormel@attbi.hormel.com (to despam, remove 2nd "hormel")



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