= Biological network
A biological network is a <graph> representing biological entities and a specified relation among them. Examples include <gene regulatory networks>, <protein interaction networks> and <metabolic networks>. The vertex and edge definitions determine the scientific meaning: physical binding, regulation, chemical conversion and correlated activity are different relations.
A directed regulatory edge $A\to B$ can record evidence that changing regulator $A$ affects expression of gene $B$. An undirected protein-interaction edge can instead record a binding assay. Neither should automatically be read as the other. Experiments also have conditions, detection thresholds and error rates, so a missing edge is not always evidence of biological impossibility.
Graph quantities such as <connected components of a graph>, <vertex degree> and <graph paths> summarize the representation. A path through regulatory edges proposes a chain of influence; it does not by itself prove a causal mechanism. Combining controlled perturbations with physical or functional measurements can distinguish alternative interpretations of the same graph pattern.
Back to article page
