Genetics: From genes to genomes - Chapter 18: How genes are regulated

Cells must obtain information about their positions relative to other cells Ligand expressed by one cell binds to a receptor expressed on the surface of another cell Juxtracrine signaling – ligand is membrane-bound and interacts with a receptor on an adjacent cell Paracrine signaling – ligand is secreted and mediates long- range (e.g. hormones) or short-range signals (e.g. Wingless and hedgehog) Different ligand/receptor combinations active different signal transduction pathways