Screening for homologous recombination in ES cells using RT-PCR.

bromide staining in detecting PCR products (Figure 3). Moreover, as expected, band intensities increase with longer duration of exposure to X-ray film (data not shown). Biotin-21-dUTP and biotin-14-dATP work equally well in labeling the PCR products (data not shown). Similarly, DNA cross-linking with baking and UV irradiation work equally well in this system (data not shown). We have also confirmed that incorporation of biotin into the PCR products does not change the size of the PCR product significantly (data not shown). The proposed method will be useful in RT-PCR or PCR experiments in which the amplification products are of known identity, yet increased sensitivity of detecting them is desired. This method requires less time and effort than hybridization protocols with a labeled probe.