Microarray results and Northern hybridization results

Microarray and Northern hybridization are reversed procedures each other and it seems that both procedures give the similar results. However, sometimes it occures that the clone, which shows the expression difference in Microarray system, does not show the same result after Northern hybridization. This might be explained by the complexity of hybridization procedure. That is, in case of Northern hybridization single DNA molecule is labelled and hybridized with the unlabelled mixture of RNAs, while in case of Microarray, mixture of target RNA constitute of so many species of molecules is labelled. During hybridization procedure, there might be the interaction within the labelled target molecules in case of Microarray system. This might cause the different results between Northern and Microarray system.