Comparison of some properties of oocytes segregating in F2 hybrids between KE and CBA/Kw inbred strains of mice

The time taken to dissolve the zona pellucida was compared with fertilizability as well as the meiotic maturation rate of the oocytes from the same (KE × CBA) F2 females. The presence of granular material in oocyte cytoplasm was also examined. It was found that for F2 females in which the zona pellucida digestion was fast, the number of fertilized oocytes was high; for F2 females with zonae pellucidae more resistant to enzyme, the number of fertilized oocytes was low. The correlation between the two characters was significant, indicating their common genetic and/or physiological control. The low or high solubility of zona pellucida did not correlate with the rate of meiotic maturation of the oocyte. This suggests separate factors controlling these two characters. A separate factor seems to control the appearance of granules in cytoplasm since their presence interfered neither with zona pellucida solubility nor with maturation rate of the oocyte.