11. Housekeeping genes

The result of a real time PCR analysis is an expression value of your target gene of interest. However, if the amount of cDNA which was used for the real time PCR reaction varies, i.e. due to an inaccurate quantification of your RNA used for the cDNA analysis or variable cDNA synthesis efficiencies, your result will also vary. Therefore it is necessary to relate your results to a control gene which is constant in the samples and the expression level of which only depends on the amount of RNA used in the cDNA synthesis rection. Such a gene is a housekeeping gene. The question is which gene to use. The cialis side effects alcohol< ansver is that no single gene can be recommended in general. It depends on your particular cell type and your application. You probably need to try out several before you find one which fulfills your criteria: its expression needs to remain constant during whatever stimulation you subject your cells to. Genes which are expressed at constant levels in cells are often structural genes metabolic genes. Therefore actin, GAPDH, cyclophillin and porphobilinogen deaminase are often used.