Table I.
Generation of Mox2+/Cre TKO and control embryos
| Embryonic stage | 5/6 embryos | TKO embryos | Total number of embryos collected |
| alive/total | alive/total | ||
| E10.5 | 8/8 | 1/1 | 44 |
| E11.5 | 6/7 | 3/4 | 44 |
| E12.5 | 8/9 | 1/2 | 32 |
| E13.5 | 7/8 | 0/0 | 40 |
| E14.5 | 2/5 | 0/0 | 13 |
| E15.5 | 1/1 | 1/2 | 24 |
| E16.5 | 0/4 | 0/0 | 20 |
| Experimental numbers | 32/42 | 6/9 | 281 |
| Expected numbers | 3/16 = 40.68 | 1/16 = 13.56 |
Alive embryos were scored as alive based on a beating heart and blood flowing through their umbilical cord. 5/6 embryos have five mutant alleles and one WT allele among the six alleles for the three Rb family genes. The overall under-representation of TKO embryos after E10.5 is statistically significant in a χ2 test (P = 0.01). All mice analyzed were in a mixed 129Sv/J:C57BL/6 genetic background.