You mated male and female heterozygous Oct4 knockout mice to study the function of this important gene. Among the progeny, one-third were homozygous wild type and the rest were heterozygous. You then repeated the cross, but this time you genotyped several embryos at different stages of early development and grouped them as either homozygous wild type (+/+), heterozygous (+/-), or homozygous null (-/-). You have summarized your results in the following table, in which the number of embryos in different groups and at different developmental stages are presented. According to these results, complete loss of Oct4 is …