Twelve-month infection with H. pylori increases the frequency of point mutations in female mice. The mutation frequency of point mutations was determined by the gpt assay in uninfected mice (white bars; 6 MPI, n = 13; 12 MPI, n = 15), H. pylori-infected males (light gray bars; 6 MPI, n = 4; 12 MPI, n = 5) and H. pylori-infected females (dark gray bars; 6 MPI, n = 9; 12 MPI, n = 11). Control mice of both sexes were grouped for this analysis. Data are mean (SEM) of mutation frequency of mice in different treatment groups. *P < 0.05.