Hello, there are so many ways to analysis the expression of gene and mRNA, but I wonder if we have a general unit to specific the expression of a gene (and this unit can use for all of methods)? I mean, if gene expression can have their own unit, based on the unit we can compare the expression of genes together, and the expression of that gene in this tissue to another tissues, and we can say it is house-keeping gene or tissue-enriched? Thank you.