Practice question

Early frog gastrula cells remain conditionally specified and highly plastic. When presumptive neural ectoderm from early gastrula is transplanted to ventral epidermal region, it adopts epidermal fate under influence of high BMP signaling from host, revealing environmental instruction. Equivalent transplants performed using late gastrula donor tissue fail to switch, continuing to form neural tissue despite epidermal cues due to stabilized expression of factors like Sox2 and epigenetic lockdown. This demonstrates progressive loss of competence and acquisition of autonomous determination with age, where early flexibility gives way to irreversible commitment after sustained exposure to inductive signals.