Heterozygosity for Nipbl causes postnatal lethality.

Data are presented on the frequencies of genotypes resulting from crosses between heterozygous mutant males and CD-1 females. The males referred to in the first row were the chimeras produced by injection of Nipbl+/? ES cells into C57BL/6 blastocysts, so in this case only progeny descended from ES cells (as distinguished by chinchilla coat color) were scored. Surviving Nipbl+/? mice from these crosses are referred to as the N0 generation; their offspring with CD-1 females are referred to as the N1 generation; their offspring with CD-1 females as the N2 generation; and so on. Note that although the ratio of mutant to wildtype animals at E17.5�CE18.5 is not significantly different from 1��1, the presence of identifiably-mutant, but not wildtype, resorbed embryos at this stage suggests that there may be a small amount of late embryonic loss.*P?P = 0.67 compared with Mendelian expectations, and P