SOUTHERN AND NORTHERN ANALYSIS

This review on Southern and Northern analysis, rather than providing step-by-step protocols, focuses on a critical evaluation of the existing experimental methods and modifications thereof. Principal parameters influencing electrophoresis of DNA/RNA in agarose gels are outlined and at the same time alterations in these parameters for optimal resolution of DNA of varying length are discussed. Further, methods for evaluating the quality of DNA/RNA size separation in agarose gels are described. Since efficient transfer of DNA/RNA from the gel onto a membrane support is critical in both methods, several experimental approaches for transfer are compared. Also discussed in this review are alternative methods for radioactive and non-radioactive labelling of DNA probes. Finally, detailed protocols are provided for an effective hybridization of Southern and Northern blots.