6.6 Gene Expression & Cell Specialization

Same DNA, different cells

Every cell in your body has the same DNA, yet a neuron and a muscle cell look and act completely differently. This is because of differential gene expression — different cell types switch on different subsets of genes. Turning on the right genes makes a cell specialized, a process called differentiation.

Controlling the body plan

Master control genes called homeotic (Hox) genes direct the overall body plan during development, telling regions of the embryo what to become. Stem cells are unspecialized cells that can still become many different cell types.

Key terms

Differential gene expression

Different cell types express different subsets of the same genome.

Cell differentiation

The process by which an unspecialized cell becomes a specialized type.

Homeotic (Hox) genes

Master genes that control the body plan during development.

Stem cell

An unspecialized cell that can differentiate into many cell types.

Same genome, different cells

All body cells share DNA; expressing different genes makes them distinct.

Try an AP-style question

A liver cell and a nerve cell from the same person have different shapes and functions. Why?

1. One lost many of its chromosomes during development
2. They contain different genes in their DNA
3. They express different sets of genes from the same genome
4. They were formed by different types of fertilization