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Housekeeping genes are genes which are always expressed because they produce proteins which are necessary for cell function. Throughout an organism with differentiated cells, it is common for the same housekeeping genes to be expressed in every cell, along with some genes which are specific to particular cell types. Hundreds of these genes have been identified in humans, and more are constantly being uncovered.
The proteins produced by a housekeeping gene vary, but are involved in some way in processes necessary to the survival of a cell. Some may be involved in sustaining cell function, while others may be involved in cell maintenance. These genes tend to produce proteins at steady rates, and errors in their expression can lead to cell death. Like a literal housekeeper, they keep the vital systems of a cell running smoothly so that it can continue to function, and they also contribute to the overall function of the larger organism.
While housekeeping genes were initially believed to be constant, some researchers have shown that the situation is actually a bit more complex. Some genetic research has shown that expression of certain housekeeping genes increases when cells become malignant, suggesting that these genes can be involved in the processes which cause cells to start running amok. In this case, overexpression of a gene may be contributing to the problem, rather than expression of a defective gene.
These genes can be useful outside the body as well. When calibrating testing systems and establishing baselines, housekeeping genes can be used as a constant, because they should always be present and should always have the same levels. If the constant is not consistent, it suggests that there may be a problem with the sample or the process being used, in which case it may be necessary to start afresh with a procedure such as polymerase chain reaction sequencing.
Geneticists are interested in housekeeping genes are part of the genome, and these genes are also topics of interest to researchers who study cell physiology. Understanding the complex reactions and genetic expression involved in the function of a cell is an important first step to understanding why cells sometimes develop problems such as multiplying too quickly, dying off, or failing to function as they should. These researchers can use a number of tools to identify housekeeping genes and explore their functions.