Post-translational modifications of lysine residues of histones can result in a series of functional changes. Lysine 79 of histone H3 (H3K79) can be methylated specifically by the Dot1 family of histone lysine methyltransferases. Although multiple developmental abnormalities in Dot1L-deficient mouse embryos have been studied, the biological function of H3K79 methylation in mammal oocytes remains unclear. Here, the distribution of Dot1L, methyltransferase of residue lys79 of histone H3 (H3K79) in mouse, and its effect on mouse oocytes meiosis were investigated to examine whether there are changes in the pattern of distribution and effect of Dot1L on mouse oocytes meiosis.