-Caveat Lector-
> > Lesbian couples could soon be giving birth to babies that are genetically
> > their own thanks to a breakthrough technique originally developed to help
> > infertile men.
This is not really a breakthrough, more of an atavisticicism, biologically speaking:
One person's research:
From
http://www.bio.metu.edu.tr/~e076054/fer6.html
}}>Begin
Parthenogenesis
Parthenogenesis is the process in which eggs are activated and develop in the
absence of a paternal genetic contribution. Parthenogenesis can be natural or
artificial. Artificial parthenogenesis involves activation of the egg by chemical
or physical means. Because the universal trigger for activation may be a Ca+2 flux,
treatments that cause such a response can. usually induce artificial
parthenogenesis. However, this only results in a partial egg activation. DNA and
protein synthesis are not stimulated to normal levels, and cell division does not
occur in A23187-activated eggs, because they lack a sperm centriole and aster. The
so-called double method for inducing artificial parthenogenesis in sea urchins
involves an initial treatment with butyric acid (which probably activates the Ca+2
flux), followed by addition of hypertonic seawater (to induce egg asters and cell
division), and can lead to complete development of parthenogenic larvae. Likewise,
although pricking a frog egg with a clean needle (thereby eliciting only a Ca+2
flux) leads to partial activation, using a bloody needle yields embryos that
develop to the tadpole stage, because the needle contains MTOCs from disrupted
blood cells.
Some animals including some flatworms, rotifers, insects, amphibians, and reptiles
reproduce by natural parthenogenesis. Natural parthenogenesis is the normal
development of an animal without a paternal genetic contribution. These animals
must overcome two important problems that are normally solved by sperm entry.
First, alternate triggers must be developed to initiate their activation program.
The methods used for this purpose are varied but usually involve physical
perturbations of the egg. In parthenogenetic wasps, for example, activation is
caused by a mechanical stimulus received by the egg as it passes out of the female
reproductive tract. The development of parthenogenetic beetles is initiated by
bacterial symbionts that enter the egg while it is in the reproductive tract. Some
parthenogenetic salamanders exhibit an unusual method of activation. They copulate
with a male of another salamander species, and the nonspecific sperm enter and
activate the egg of the parthenogenetic species. The sperm nucleus subsequently
degenerates in the egg cytoplasm and does not contribute genetic material to the
embryo. Second, parthenogenetic organisms must develop a means of attaining the
diploid chromosome number in the absence of pronuclear fusion. This problem is
usually solved by imposing an extra round of DNA synthesis and chromosome
duplication either before meiosis or during the early cleavage of the zygote.
Natural parthenogenesis has not been demonstrated in mammals. Mammals may not have
evolved parthenogenesis because, unlike most other animals, genetic contributions
from both the sperm and egg are required for development.
End<{{
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