Heterochromatin loss appear uniformly in diverse oocytes populations: IHF staining was performed on ovaries cryosections from young (2‐month‐old) and old (9‐month‐old) female mice. Loss of heterochromatin was detected in the intact oocytes in both (a) H3K9me2 (t test < 0.0001, animals used for experiment N
young = 3, N
old = 3) and (b) H3K27me3 staining. (MW = 0.0008, animals used for experiment N
young = 3, N
old = 3). Staining of MI metaphase chromosomes and staining intensity analysis from young (2‐month‐old) and old (9‐month‐old) females (see Methods) was performed for the following markers: (c) H3K9me2 (t test p = 0.008, animals used for experiment N
young = 3, N
old = 5) and (D)H3K27me3 (MW p < 0.0001, animals used for experiment N
young = 3, N
old = 4)