In a normal Drosophila embryo, a gap gene called Krüppel is expressed in the anterior end because it is activated by Hunchback protein, and this region contains a high level of Hunchback.

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Krüppel, a gap gene in Drosophila, is actually expressed in the middle region of the embryo, not the anterior end. It is regulated by the concentration of Hunchback protein, which is higher in the anterior, but Krüppel expression is activated in a specific intermediate zone where the Hunchback concentration is optimal, not at the highest levels of Hunchback found in the anterior.

In a Normal Drosophila Embryo, a Gap Gene Called Krüppel