Abstract: The invention relates to a method for preparing a probe, thus prepared probe, and the use of such a probe for selectively choosing sequence for nucleic acid diagnostic purposes, using preferably homogenous solutions. The invention is based upon a great number of probes having different sequences and lengths which all are complementary to different parts of the nucleic acid to be detected, which probes are synthetised on a solid matrix. The signal which they provide in non-hybridized condition is monitored, whereupon the nucleic acid to be detected is added, and the signal is monitored again. Those probes that show the most significant difference in signal are those, from a sensitivity point of view, that are the most suitable one.