Final answer:
Mutations in Hox genes, which could mistakenly be referred to as Phox genes, result in major developmental changes such as body parts growing in the wrong places. These highly conserved genes determine an organism's body plan and are critical during embryonic development.
Step-by-step explanation:
Mutations in the Phox gene, which is likely a typo for 'Hox gene', result in significant changes to the body plan and structure during embryonic development. For instance, a fruit fly with a Hox gene mutation may exhibit a leg growing out of its head where its antenna should be, signifying how these genes control the placement of body parts. In general, Hox genes are a series of regulatory genes that play a crucial role in the development of the body's segmentation and appendage placement, determining structures such as limbs, antennae, and the overall head-to-tail organization of the animal during its embryonic development.
If a Hox gene is mutated, the instructions that normally ensure specific body parts develop in certain locations can go awry, leading to the aforementioned abnormal growths. In a broader sense, these genes are vital for establishing the basic blueprint of an organism's body plan. They are highly conserved and found across a wide range of organisms, indicating their fundamental role in animal development.