Figure 1.
Dietary folic acid supplementation produces a true rescue of Cd/Cd embryos. (A) Distribution of embryonic phenotypes as a percentage of all embryos scored at E12.5 from dams maintained on diets containing defined amounts of folic acid (FA) (parts per million, ppm = mg/kg chow). On a 0 ppm FA diet, homozygous phenotypes accounted for 22%, nearly all of the expected 25% for a Mendelian distribution of an autosomal recessive mutation. However on a 10 ppm FA diet, 7.5% displayed embryopathy (30% of the expected 25%). Compared to embryos on a 4 ppm FA diet, the exencephaly encountered on a 10 ppm FA diet was reduced more than half. (B) Cd/Cd embryos are not lost prior to implantation. The genotype distribution observed for E12.5 embryos maintained on defined FA diets showed the expected Mendelian pattern of 1:2:1 for a heterozygous parental cross. Data from Carter et al., 1999