In labs, scientists have introduced mutations in fruit fly genomes to create flies with legs growing where their antenna should be. Explain why changing the nucleotides in the Hox genes could cause this.

The mutations that lead to the growth of legs in place of the head are all called homeotic transformations. The defects in the Hox or Homeotic box gene leads to such abnormal growths. The work demonstrated that only certain special cells can take up the identity of becoming a leg, head or the thorax. This supports the idea that every cell in the developing embryo carries the information to differentiate into various body parts like the head, legs, and the thorax, etc. The growth of legs in place of the antennae is because the cells coding the antennae didn't function due to mutations in the Hox gene, while the cells that were coding the legs took over that segment of the body and made the legs.

The Hox genes control how body parts are shaped and arranged. Genes are sections of DNA that code for a particular protein; they give the organism its visible traits. Altering the nucleotide sequence in this section of DNA alters protein synthesis. This change causes a completely different body part to grow.