I am pondering a biological question that came from reading about cloning and associated techniques. Amazingly even my wifes university biology reference books (big ones too…) don’t even decribe how identical twins actually happen.
OK, what do I know? When a female egg cell is fertilized (I’m sure there are other sites that can describe how this happens…) it becomes a ZYGOTE. This then goes through a rapid division process called CLEAVAGE to about 32 cells when it is known as a MORULA, and each individual cell is called a BLASTOMERE.
Each BLASTOMERE has different components of egg cytoplasm, so even though they have the same DNA (don’t know how this happens either as there is no description on how the genetic information is divided or shared) it is the cytoplasm components that dictate different developmental paths for the cells.
So are identical twins formed due to the first cleavage process not just dividing into two cells but actually seperating into two discrete zygote-like cells that then continue the development process individually so that you have two identical twins?
This kinda makes sense to me. So if this is the case, then at what point does the capacity for blastomere cells to reproduce the whole human finish? Is it 4, or 8 or what?
Obviously a single womb could not handle such a number, but since we are pretty adept at extracting fertilised cells and then embedding them successfully elsewhere…