For the purposes of the present invention, the term ???high stringency conditions??? is to be understood as referring to such conditions applicable to probe hybridisation (eg conditions which: (1) employ low ionic strength and high temperature for washing, for example, 15 mM NaCl/1.5 mM sodium citrate/0.1% NaDodSO4 at 50??? C.; (2) employ, during hybridisation, a denaturing agent such as formamide