Table 4. Many Poldip2 knockout mice are viable.

	Observed counts		Observed total	Expected total
genotype	male	female		1:2:1
+/+	39	41	80	76.25
+/-	89	81	170	152.50
-/-	24	31	55	76.25
Total	152	153	305	305

Pups produced by crossing two Poldip2^+/- (excised Poldip2 heterozygous) mice were genotyped at weaning, as in Fig 6. Genotype counts were significantly different from the expected 1:2:1 Mendelian distribution (P<0.05), due to a deficit in -/- mice (18% vs. 25%). However, this proportion of live homozygotes was higher than in gene trap mice (3% at weaning), suggesting that perinatal mortality is less severe in the new model.