Final answer:
The alteration of a regulatory sequence in the Antennapedia gene caused by a mobile genetic element results in the development of legs on the head instead of antennae.
Step-by-step explanation:
The alteration of a regulatory sequence of the Antennapedia gene, caused by the insertion of a mobile genetic element, leads to a change in the expression of the gene. In the case of the Antennapedia gene, the alteration results in the development of legs on the head instead of antennae.
This alteration occurs due to the disruption of the gene's regulatory sequence by the mobile genetic element. This, in turn, affects the binding of transcription factors to the promoter region of the gene. The affected binding sites result in a change in the rate of transcription, leading to the abnormal development observed in the Antennapedia mutant.