6.6 Gene Expression and Cell Specialization

Nearly every cell in your body has the same DNA. Neurons and liver cells differ because they express different subsets of genes, controlled by different transcription factors.

Homeotic (Hox) genes control body plans during development; mutations can put legs where antennae should be in flies.

Morphogen gradients and cell-to-cell signals tell embryonic cells where they are. Apoptosis sculpts structures (separating fingers). Small RNAs fine-tune timing.

Differentiation = differential gene expression, not different genes.

Worked example: Why does a skin cell not make hemoglobin? → The hemoglobin gene is present but not transcribed; the needed transcription factors aren't active.