<div>Background: Vitamin A has potentially harmful effects on the development of chick embryos even at very low dose concentration. Vitamin A different doses cause embryotoxic and teratogenic effects on the developing of the chick embryo. Hence, due to teratogenicity of this vitamin it can be used with utmost caution during pregnancy. &nbsp; &nbsp; &nbsp; 
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Methods: Fertile chicken eggs (obtained from local hatchery) were injected with three doses of Vitamin A (15 IU/ml, 30 IU/ml, 75 IU/ml) into the center of the egg yolk. Morphometric parameters as mortality rate, body weight (g), crown rump length (mm) of embryo and Frequency % of different anomalies gross malformations were measured. Whole chicken samples were taken by 4th, 8th and 18th incubation day. Daam, Hox and Tbx genes expression profile were analyzed. 
 
Result: Dose-dependent defects and embryo lethality in the chick embryos developed when exposed to higher concentrations. Our study record for the first time the duplication in the heart, brain and eye. Also showed duplication of the neck forming S-shaped showed in some malformed chick embryos. The three investigated genes showed different fluctuations confirming the malformations detected.</div>

Impact of Vitamin A on the Expression Profile of Development-Controlling Genes in Chick Embryos