FIG. 4.

In vivo fertilization analysis. C57BL/6 × CBA F₁ females were superovulated and mated with Nl1^+/+ or Nl1^−/− males. Embryos were collected at day 1 postconception and cultured in vitro for 4 days. Embryo development was monitored by daily microscopic analysis. Bars labeled −/− indicate eggs fertilized by Nl1^−/− males, while bars labeled +/+ correspond to eggs fertilized by wild-type males. Chi square (χ²) and Jonkheere-Terpstra (JT) analyses revealed that the distribution of developing embryos was statistically different at each day (day 1: χ², P < 0.0001, and JT, P < 0.0001; day 2, χ², P < 0.0024, and JT, P < 0.0003; day 3.5, χ², P < 0.0001, and JT, P < 0.0001; day 4.5, χ², P < 0.0001, and JT, P < 0.0001).