Students build simple clay or play dough models of the zygote, morula, blastula, and gastrula to visualize where stem cells come from and how cell potency changes from totipotent to pluripotent to multipotent. The activity also introduces the source of embryonic stem cells and contrasts them with adult stem cells.

• See links below for method and activities.

📄 Stem Cell Development - www.nwabr.org: https://www.nwabr.org/sites/default/files/LESSON_1.pdf

• Make one batch of homemade play dough and add food coloring at each stage to show progressive differentiation.
• Extend with a chart comparing sources, potency, advantages, and limitations of embryonic versus adult stem cells.

• Use caution with paper clips or similar tools when cutting models; points can puncture skin.
• Check for latex, fragrance, or dye sensitivities in modeling materials; provide alternatives if needed.
• Keep small pieces away from young children to prevent choking.

• What is the difference between totipotent, pluripotent, and multipotent cells? (Totipotent can form all body tissues and placenta; pluripotent can form any body cell but not placenta; multipotent is limited to a range within one tissue or germ layer.)
• From which stage are embryonic stem cells isolated in this model? (The inner cell mass of the blastula.)
• What happens to the blastula if the inner cell mass is removed? (It is destroyed and cannot continue development.)
• How can identical twins arise based on early development? (One or more cells separate during early cleavage or morula stage and each develops into an individual.)
• Which organs or tissues derive from each germ layer? (Endoderm: digestive and respiratory linings; mesoderm: muscle, bone, blood, heart; ectoderm: skin and central nervous system.)
• Why are adult stem cells considered multipotent? (They are already committed to a germ layer or tissue and can produce only related cell types.)
• What is one advantage and one limitation of embryonic stem cells compared with adult stem cells? (Advantage: broader developmental potential and easier to culture; limitation: ethical concerns about destroying the blastula.)