Comparative Analysis of Effects of Urea and Trypsin on Human Chromosome Banding

Obtaining good banding pattern of human chromosomes is always a critical step in cytogenetic analysis. Effects of various concentrations of urea and trypsin on human chromosome banding were studied. Maximum percentage of chromosomes showing optimal number of demonstrable bands was obtained with 5.12mg% freshly prepared trypsin solution (pH 6.8) in 16 to 18 seconds for aged slides as well as with 8 mol/L fresh urea solution in 30 to 90 seconds for freshly prepared slides. There was no resolution difference at these concentrations. The percentage of chromosomes showing optimal number of demonstrable bands were decreased by 41.3% and 84.8% on one hour and two hours storage of 5.12mg% trypsin solution at 370C respectively with severe effect on band resolution. While no difference was found on one hour and two hours storage of 8 mol/L urea solution at 370C and even on storage for a week at 40C there is only 1.6% decrease without affecting band resolution. Thus urea method offers an advantage in having better stability of solution and non requirement of slide ageing while longer urea treatment time is a disadvantage