HL A2.2 Cellular Differentiation

Cellular differentiation is the process by which unspecialized cells become specialized through specific patterns of gene expression.

All cells in a multicellular organism have the same DNA, but different genes are switched on or off in different cell types.

Totipotent cells (zygote and early embryo) can form all cell types, including extraembryonic tissues.

Stem cells can self-renew by mitosis and differentiate into specialized cell types.

Differentiation proceeds through ectoderm, mesoderm, and endoderm, each producing specific tissues and organs.

Once a cell is fully differentiated, it usually cannot revert to another cell type.

Environmental factors (e.g. temperature, diet) can alter gene expression without changing DNA sequence, affecting phenotype.