When isolating RNA, it helps to have a rough idea of how much total or poly(A) RNA can be recovered from a given amount of tissue or cells. It is also beneficial to know rough expression levels for rare to moderately abundant transcripts when performing Northern analysis or RPAs, e.g. in order to set up a meaningful standard curve for absolute quantitation, or to know how long of an exposure is reasonable. These numbers provide a point of reference against which experimental procedures and results can be checked. Tables 1 and 2 provide general guidelines for estimating RNA yields from a variety of cells and tissues. Remember that RNA yields from analogous tissues in different organisms can also vary:
