Q.Write a short note on stem cell technique.

Stem Cells and Their Potency

Stem cells are unspecialised cells capable of self-renewal and of differentiating into specialised cell types. They are graded by their potency — the range of cell types they can form.

• Totipotent — can form every cell type of the body plus extra-embryonic tissues; e.g. the zygote and early cleavage cells.
• Pluripotent — can form all three germ-layer cell types but not a whole organism; e.g. cells of the inner cell mass of the blastocyst.
• Multipotent — can form a limited range of related cell types; e.g. haematopoietic (blood) stem cells.
• Unipotent — can form only one cell type; e.g. a basophil/muscle progenitor cell.

Thus potency decreases as differentiation proceeds: totipotent → pluripotent → multipotent → unipotent. Matching each potency level to its example (zygote, inner cell mass, haematopoietic cells, progenitor cells) is a common examination task. …