housekeeping gene

A housekeeping gene is one that keeps the lights on. Every cell, whatever its specialty, needs basic ongoing chores done — making energy, building proteins, copying DNA — and the genes for these chores are expressed steadily, all the time, in essentially every cell type.

Because their products are needed continuously, housekeeping genes tend to have promoters that fire reliably and are less tightly switched by tissue-specific signals. They contrast with regulated or tissue-specific genes, which are turned on only in certain cells or under certain conditions, such as the gene for a digestive enzyme made only in the pancreas.

Their dependable, roughly even expression makes housekeeping genes useful as reference points in the laboratory: when scientists measure how much another gene is expressed, they often compare it against a housekeeping gene assumed to stay constant. In practice no gene is perfectly constant across all conditions, so this assumption is checked rather than taken for granted.