Practice question

Autonomous specification implies blastomere fate predetermined by unequally partitioned factors during cleavage rather than later induction. In large micromeres, vegetally localized maternal proteins including Disheveled prevent formation of β-catenin destruction complex, accumulating β-catenin in micromere nuclei. This activates Pmar1 transcription factor, which represses HesC repressor, releasing skeletogenic genes. These determinants are synthesized and deposited during oogenesis and differentially segregated by unequal cleavage, not induced later by neighboring cells. Transplantation and culture experiments confirm retained skeletogenic fate in vitro. Thus inherited maternal determinants, rather than cell-cell signals or environmental stimuli, drive micromere autonomous behavior.