Final answer:
Hedgehog and Engrailed genes are expressed during embryonic development and belong to the Hox gene family. They are responsible for determining the body plan of an animal. Wingless is involved in the development of the skin and nervous system.
Step-by-step explanation:
Hedgehog and Engrailed are genes that are expressed during embryonic development in animals. These genes belong to the Hox gene family, which are responsible for determining the general body plan of an animal, including the number of body segments and the placement of appendages. In mice, Hox gene expression occurs in certain body segments at certain stages of development and is conserved in humans as well. For example, Hox genes are expressed in specific body segments in both mice and humans, as shown in Figure 27.5.
Wingless, on the other hand, is a gene involved in the Wnt signaling pathway. It signals ectodermal cells to form epidermal cells and the neural plate. This gene is important for the development of the skin and the nervous system.