Either of the aforementioned transgenic non human animals can be bred with {HEAD ~ animals} having inactivated heavy and light chain loci to produce a transgenic non human animal that produces a fully human antibody and is incapable of producing {TAIL ~ an endogenous antibody} 
is incapable of producing
Either of the aforementioned transgenic non human animals can be bred with { HEAD ~ animals } having inactivated heavy and light chain loci to produce a transgenic non human animal that produces a fully human antibody and is incapable of producing { TAIL ~ an endogenous antibody }
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