Final answer:
Homeotic genes, also known as Hex genes, play a crucial role in controlling the development of the body plan in animals. The organization and expression of Hex genes are highly conserved between fruit flies and mice, indicating a shared evolutionary history. This conservation of Hex gene function suggests a common ancestry and emphasizes the importance of these genes in determining the body plan of different animal species.
Step-by-step explanation:
The evolutionary conservation of homeotic gene organization and transcriptional expression can be observed in fruit flies (Drosophila) and mice. Homeotic genes, also known as Hex genes, are a group of highly conserved genes that control the development of the body plan in animals. In fruit flies, there is a single cluster of Hex genes that determine the anterior to posterior body plan. In mice, these genes are duplicated into four clusters: Hex-A, Hex-B, Hex-C, and Hex-D.
In both fruit flies and mice, the expression of Hex genes occurs in specific body segments at certain stages of development. This shared pattern of gene expression indicates an evolutionary conservation of Hex gene function. For example, the expression of Hex genes in the developing head and thorax segments of fruit flies is homologous to that of the corresponding segments in mice.
The conservation of Hex gene organization and transcriptional expression suggests a common ancestry and highlights the importance of these genes in determining the body plan across different animal species.