A ready-to-use kit for the PCR amplification of nucleic acids is described, comprising at least one vessel into which a master mix comprising the salts, the buffer and the deoxynucleotide triphosphates required for the PCR amplification is prealiquotted, the said master mix being mixed with an effective amount of an inert temperature controllable polymer such that the final mixture thus formed is in the liquid phase at a predetermined temperature and in the gel phase at a temperature lower than a second predetermined temperature.
