Fig. 4. In vivo fertilization assay. The fertilization rate, fertilization index and sperm bound per egg were compared for wild-type and knockout eggs in six experiments (n=6) using a total of 158 wild-type oocytes and 71 Pig-a^–/– oocytes. (A) The fertilization rate was 54±12% in wild type eggs and 6±6% in Pig-a^–/– eggs; P=0.004. (B) The fertilization index was 0.63±0.14 in wild-type eggs and 0.07±0.07 in Pig-a^–/– eggs; P<0.002. (C) The number of sperm bound per egg in wild-type eggs is not significantly different from wild-type and Pig-a^–/– eggs (P=.09). Asterisks indicate values significantly different from the control. Error bars represent s.e.m.