In molecular biology, Housekeeping genes are typically constitutive genes that are required for the maintenance of basic cellular function, and are expressed in all cells of an organism under normal and patho physiological conditions. Although some housekeeping genes are expressed at relatively constant levels (such as HSP90 and Beta-actin), other housekeeping genes may vary depending on experimental conditions.
In a study involving cardiac stem cells ACTB and GAPDH were found to be the most consistent, while β2M, HPRT-1 and RPLP-1 varied significantly between neonatal and adult cardiac cells. The origin of the term "housekeeping gene" remains obscure. Literature from 1976 used the term to describe specifically tRNA and rRNA. Interpreting gene expression data can be problematic, with most human genes registering 5-10 copies per cell (possibly representing error). Housekeeping genes are expressed in at least 25 copies per cell and sometimes number in the thousands.
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“The cart before the horse is neither beautiful nor useful. Before we can adorn our houses with beautiful objects the walls must be stripped, and our lives must be stripped, and beautiful housekeeping and beautiful living laid for a foundation.”
—Henry David Thoreau (1817–1862)