In article <cummins-1811961445240001 at vetmac3.murdoch.edu.au>, cummins at central.murdoch.edu.au (Jim Cummins) writes:
>In article <328E5E4F.DFC at mit.edu>, Bugra Giritlioglu <bgiritli at mit.edu> wrote:
>>> I am curious to see what people know about the possibility of same-sex
>> parenting, i.e. the possibility of achieving fertilization by combining
>> the genetic material from two sperms (or two eggs).
>>This probably would not work as differential methylation during genomic
>imprinting in the gonad treats the male genes differently from the
>female. Male genes acting in the embryo serve to maximise growth and
>placental function at the expense of the maternal organism. Female genes
>serve to mimimise growth and preserve the maternal interest. One would
>have to de-imprint the genes to have same-sex fertilization. Occasionally
>one gets a dispermic egg developing without the egg's genes participating
>- the end result if a hydatidiform mole - a monster. Ocasionally eggs
>will activate spontaneously in the ovary and result in an ovarian
>teratoma. So we DO need two genders!
In the bivalve Mulinia lateralis, development of gynogenetic individuals
obtained by activation of the egg with UV-irradiated sperm (DNA is destroyed)
and blockage of polar body extrusion is normal. Polar body and egg should have
different imprinting patterns than sperm, and probably share the same pattern
between them. Your argument of imprinting is not valid. Actually, I wonder if
imprinting has been demonstrated in other organisms than mammals (I think it
hasn't). Gynogens in bivalves indicate that you do not need two genomes of
different sexes to make a viable embryo. Maybe you need two sexes, if you
consider that activation of the egg is carried out with sperm (although
irradiated). But even that is not true: activation of the egg can be achieved
by treatment with potassium chloride in Mulinia.
Diploid bivalves could be obtained fusing eggs if the fusion activates
development at the same time. Otherwise you would need sperm, potassium
chloride or other means to activate the eggs before, while or after fusion has
occurred. Nobody has tried that, I guess.
I have to recognize that most attempts of obtaining viable gynogens have not
been successful, because animals dye during the larval phase or earlier. But we
do not know if that is due to the treatment or to more fundamental reasons. One
of these fundamental reasons is simply that deleterous genes are put in ho
ozygosis by gynogenesis.
P.S.: maybe it wouldbe better to continue with this in bionet.molbio.molluscs.
That newsgroup neeeds some activating agent, and I don't believe that potassium
chloride would help in this case!
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