As already reported in a previous chapter of this book, it is possible to extract and analyze RNA from fixed- and paraffin-embedded tissues (seeChapter 5 ). For many purposes, a simple qualitative analysis of the presence of a specific RNA in tissues may be sufficient, for instance, to establish the persistence in tissues of the genome of an RNA virus. However, when gene expression levels are needed, quantiation of the specific mRNA is an important task.
