Western blot technique is done for-
Visualization of a specific DNA or RNA fragment among the many thousand of contaminating molecules requires the convergence of a number of techniques collectively termed the blot transfer.

Southern blot → Detects DNA
Northern blot → Detects RNA
Western blot → Detects proteins (proteins are separated by electrophoresis, renatured and analysed for an interaction by hybridization with a specific labelled DNA probe).
Mitochondiral RNA
Double strand DNA
r-RNA
Protein