Human chromosome hot points. V. The effect of four nucleosides on chromosomes in folate-free medium.

Human lymphocytes from 18 healthy adults were cultured in minimal essential medium without folic acid. The addition of 4 mM cytidine or 1 mM guanosine to cultures 24 h prior to harvest produced a statistically significant increase in hot point 3p14 breaks. An excess of 3 mM adenosine or thymidine had no such effect on the hot point. The mechanism of the effects of nucleosides on hot points was discussed.