Re: Question about avian sex chromosomes

[Dora Smith <villandra@austin.rr.com>]

OK, new Biology 101.   Since birds are dinosaurs, I don't know when I'm
going to quit getting startled...

How do fish do being male and female without sex chromosomes?

Yours,
Dora Smith
Austin, Texas
villandra@austin.rr.com
----- Original Message -----
From: "Mickey Mortimer" <Mickey_Mortimer111@msn.com>
To: <dinosaur@usc.edu>
Sent: Saturday, July 03, 2004 7:49 PM
Subject: Re: Question about avian sex chromosomes


> Dora Smith wrote-
>
> > As far as I know, all higher living things, let alone all higher
animals,
> > that reproduce sexually, have a female with two X chromosomes, and a
male
> > with one X chromosome and one Y chromosome.
> >
> > Do birds do sex chromosomes differently than mammals do?   If so, since
> > dinosaurs and mammals share common ancestors, how could such a thing
have
> > happened?
>
> A lot of different organisms have sex chromosomes (not just "higher"
> organisms or "higher" animals), but it's not always like in mammals with
XX
> and XY.  Some plants, insects (eg. Drosophila), some lizards and turtles
are
> like mammals, with the male having the heterogenic chromosomes.  But in
> birds, snakes, some lizards, some amphibians and other insects (eg.
> lepidopterans), the females are heterogenous.  Some apmhibians and most
fish
> lack sex chromosomes.  As you can see, birds developed their system
> separately from mammals.  I'm pretty sure their most recent common
ancestor
> lacked sex chromosomes of any sort.
>
> Mickey Mortimer
> Undergraduate, Earth and Space Sciences
> University of Washington
> The Theropod Database - http://students.washington.edu/eoraptor/Home.html