Re: Parthogenesis in birds.
- From: Ron O <rokimoto@xxxxxxx>
- Date: Mon, 13 Jul 2009 05:02:37 -0700 (PDT)
On Jul 13, 3:16 am, Ernest Major <{$t...@xxxxxxxxxxxxxxxxx> wrote:
In message
<8d136e3e-400a-42e4-9072-5c83dbb6a...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
troll <trolid...@xxxxxx> writes
I have grown more and more skeptical that anything
useful can ever be derived from browsing through
usenet.
Overall, it is simply an endless stream of persons
disconnected from reality posting false information,
countered with an endless stream of useless and
uninformative insults, followed by an endless number
of false information posted ad nauseum.
The search engines are also useless. They
will always generate an infinite number of hits
to newsy factoids, that usually don't actually
say anything, and don't bother to care whether
the information that they are presenting is true
either. They will also show a large number of
hits to advertisements.
Maybe if I only use search engines that only
link to .edu domains.
You shouldn't boast about your lack of google-fu ...
but tryhttp://www.google.com/advanced_scholar_search
andhttp://www.google.com/advanced_book_search
The question is, how common is parthogenesis
in birds? Reasonably, if a bird lays an egg, it
has dedicated a high level of resources to egg
production, relatively more than that of a mammal,
since all of the food for the growing chick is in the
egg.
If a cell inside the egg is not fertilized properly,
those resources go to waste if nothing develops
in the egg. This would seem to help select for
a meiosis bypass or alternate recombination to
prevent the wastage of resources. I would imagine
that the bird simply eats the egg if it does not grow
a chick.
Parthogenesis does happen in some reptiles. What
about different bird species? Is it very common in
some of them or is it generally rare?
Parthenogenesis is fairly common is some strains of turkeys. A cursory
examination of the results from Google Scholar finds references to it
occurring in chickens, Chinese painted quail and zebra finches.
Getting live parthenogenetic chicks is rare. This likely has
something to do with the genetic load, as well as a genetic tendency
to mess up meiosis. Domestic turkeys are fairly inbred and probably
went through a severe bout of purifying selection. Only one
chromosome set is doubled, so you get sort of an instant highly inbred
line except for residual recombination resolutions. That is why all
parthenogenetic chicks or poults are males. Males are ZZ (equivalent
to the human XX) and females are ZW where the W is the small sex
determining chromosome. So WW female embryos die and so do any
homozygous lethals or embryos that are homozygous for enough
detrimental loci to kill the embryo. To maintain the turkey line they
had to cross the males back to the female parents. I got to see this
line of turkeys at Guelph during the 1994 World genetic conference,
but I think that they have discontinued the line due to funding
restrictions.
Ron Okimoto
I know that it is rather unlikely that I could get any
useful or informative information from this post.
I thought I might try, however.
--
alias Ernest Major-
.
- References:
- Parthogenesis in birds.
- From: troll
- Re: Parthogenesis in birds.
- From: Ernest Major
- Parthogenesis in birds.
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