Human bone marrow colony formation in diffusion chambers. Normal values.

In situ hybridization techniques have previously employed a series of manipulations to effect denaturation of chromosomal DNA and reannealing of DNA-RNA hybrids. This report presents a new protocol which combines the denaturation and reannealing processes. DNA is heated in a solution of 50% formamide, 50% 4 × SSC containing the RNA to be hybridized. After l h at 70 °C the preparation is slowly cooled to 37 °C over a period of 6 h and incubated at 37 °C for an additional 10 h. This technique eliminates the possibility of premature reannealing of the DNA while employing hybridization conditions which, in vitro, lead to accurate base pairing.