Representative histograms demonstrating telomere length in murine bone marrow MNCs. Telomere length was measured by hybridization of a FITC-labeled peptide nucleic acid probe to telomere repeat sequences in bone marrow MNCs from (A) wild-type and MSH2^–/– mice not receiving transplants and (B) P2 mice recipients of serially transplanted 100% MSH2^–/– cells in the presence or absence of TMZ treatment. In panel A, there was no significant difference in telomere length (mean fluorescence intensity) between wild-type and MSH2^–/– mice. In panel B, the average mean fluorescence intensity was similar in treated and untreated mice receiving MSH2^–/– cells; however, TMZ-treated mice had a more heterogeneous distribution of telomere length. In 3 mice tested, there was a significant increase in the breadth of telomere length distribution; P = .01 (Kolmogorov-Smirnov [K-S] test that calculates the difference between the summation of 2 curves). Absolute values of telomere length in panels A and B cannot be compared because samples were measured separately.