These include in vitro
editing of primordial germ cells that are subsequently transmitted through germ - line chimeras to produce genome
edited offspring, and
direct injections to developing
embryos, creating germ - line chimeras in ovo (in the egg), which can then be bred to produce genome
edited offspring.
They included cloning (somatic cell nuclear transfer, accomplished in many placental mammals), stem cell gametogenesis (has been done in mice),
direct engineering of early stage
embryos (has been done in several mammals), embryonic stem cell
editing, and primordial germ cell (PGC)
editing.