Practice question

Classic Spemann and Mangold style cross-species grafts test specificity of induction and origin of pattern information. Presumptive ectoderm from early frog gastrula transplanted into newt gastrula mouth region still forms frog-specific keratinized mouth structures with characteristic papillae, cement gland histology and mucus composition, rather than newt-type morphology. Inductive signal from underlying pharyngeal endoderm and cranial neural crest triggers mouth formation, but response genome determines species-specific shape and cytology. Regional specificity would mean location determines structure irrespective of donor, autonomous specification would mean differentiation without host signals. Here host provides location cue, donor genome executes species-specific program, illustrating genetic specificity.