Re: Probability of survival with early embryonic cell separation

dear Flavio, 
finally the answer!

A cell obtained from a zygote can successfully generate a complete organism under 
the appropriate conditions: it can, but it depends from which organism and from 
which cell of the zygote you choose.

E.g., there are a lot of studies on sea urchin and frog (Xenopus laevis) on this 
subject. You can easily find them in any book of developmental biology. Within 
this biological system, at the beginning of this century, Wilhelm Roux and H. 
Driesch demonstrated that only when you choose (from the zygote) the cell that 
contains specific determinants can you generate from this cell a complete 
organism (if you choose the wrong cell you obtain only a ball of undifferentiated 
ectodermal tissue). During the last two decades, the nature of these determinants 
was partially uncovered: they are maternal mRNA's, mRNA produced by the mother of 
the zygote and stored in the oocyte (the egg cell) before fertilization. These 
maternal mRNA's are translated into protein that regulate the early stages of 
development of the embryo.

To answer your question regarding biological system that are more complex, it 
is possible to say some things about mouse and man, the two best known mammals.
The existence of twins implies that an isolated mammalian blastomere (as
the cells that form the embryo in the first stages of the development are called) 
can give rise to an entire embryo. In 1952, Seidel supported this notion by 
destroying one cell of a 2-cell rabbit embryo. The resulting blastomere was able 
to develop into a complete adult. Even a single blastomere of an 8-cell mouse 
embryo can develop successfully into a complete adult (Kelly, 1977).

That's all (for the moment!)
I appreciate your interest in the field of developmental biology: I think that it 
is one of the more interesting and quickly developing field in biology!

I should repeat that you can find more information about that in any book of 
developmental biology (I studied "Developmental biology" by S. Gilbert, Sinauer 
Assoc. Inc.).

Best regards

Dr. Luca Faoro   

P.S.: Remember that (today) human cloning is illegal in Brazil!!
Bye