Since many life processes, such as development and reproduction, depend on differential gene expression, the spatiotemporal pattern of gene expression is of prime biological interest. Accordingly, the concepts of the mRNA differential display (DD) and RNA fingerprinting techniques (1 ,2 ) promised a breakthrough in molecular biology, because they circumvented some severe limitations of traditional methods, such as differential screening and subtractive hybridization, during the analysis of differential gene expression.
