A bicoid is a gene, in Drosophilia and related fly species, which specifies which end of an egg will be the anterior and become the fly's head by setting up a concentration gradient of the bicoid protein.
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Factors in the zygote that determine early development by there positioning. Google bicoid.
This is called bicoid mutant phenotype, and is caused by a maternal effect gene which is a gene that, when mutant in the mother, results in a mutant phenotype of the offspring regardless of the offspring's genotype.