Assuming, of course, that the use of the same bases and amino acids and the same genetic code had already evolved independently. You see, if I swap a gene from _your_ mitochondria to _your_ nuclei, it simply won't work. Vertebrate mitochondria read one of the "universal" stop codons as tryptophan,
Yes, but we were talking about the possibility of gene transfer between two or more non-monophyletic *microbes* at ~4 Gya. I am assuming that, with these simpler organisms, the "rules" governing genetic processes are a bit lax compared to those in vertebrates.