Table 1. Survival of PTBP1 null mutants.

		genotype			ratio PCR		ratio IF
age	method	wt	het	hom	wt/het	hom/het	hom/het+wt
E6.5	IF	19		5			0.26
E7.5	PCR	5	12	5	0.42	0.42
E7.5	IF	3		3			1.00
E8.5	IF	7		2			0.29
E12.5	PCR	8	17	0	0.47	n/a
E16.5	PCR	1	3	0	0.33	n/a
3 weeks	PCR	25	44	0	0.57	n/a
				expect:	0.50	0.50	0.33

The table summarises the genotype of embryos during gestation as determined by PCR or immunofluorescence (IF), the latter of which cannot distinguish between wild-type (wt) and heterozygous (het). The last viable homozygous (hom) embryos were detected at day 8.5 of embryonic development (E8.5). No homozygous mutants were found at E12.5 or later. Genotype ratios observed and expected are shown on the right. While they are close to the expected Mendelian ratio for experiment with several litters, random variations and deviation from the expected ratios are larger in single litter experiments.