Practice question

Developmental potency narrows progressively as epigenetic restrictions and lineage-specific transcription factors accumulate. The zygote and early morula are totipotent, producing embryo plus placenta. With blastocyst formation, inner cell mass becomes pluripotent, forming all three germ layers ectoderm, mesoderm, endoderm but not trophectoderm. Subsequently, tissue-specific multipotent stem cells such as hematopoietic stem cells arise, limited to lineages within one germ layer. Finally, unipotent progenitors differentiate into single cell types like erythrocytes or spermatids. This totipotent to pluripotent to multipotent to unipotent hierarchy reflects irreversible chromatin condensation and loss of plasticity.