RNA analysis () RNA can be purified in either total RNA or poly(A)-selected RNA (mRNA) form. mRNA comprises less than 5% of cellular total RNA. Generally speaking, for most RNA related applications, total RNA is sufficient for most requirements. Two specific applications, cDNA library construction and cDNA labeling for microarray require isolation of mRNA. Around 30ug of mRNA equels 1mg of total RNA.
Northern blot hybridization is used for determination of mRNA molecular weight and relative abundance. It is commonly performed using total RNA. Dot hybridization can not determine the size of mRNA species but can assay the quatity of the RNA target. Ribonuclease protection assay is also used to assy the abundance of mRNA species. RT-PCR is the most sensitive method for quantitatively measureing of mRNA expression level.