[Campbell Biology P.513] Based on Figure 21.20 and the accompanying text, what is a key diff... | Practice Question

Based on Figure 21.20 and the accompanying text, what is a key difference in how Hox genes specify segment identity between the brine shrimp Artemia and the grasshopper?

  • A: In Artemia, Hox genes are expressed in discrete regions, while in grasshoppers, they are expressed together in one region.
  • B: In both organisms, each Hox gene specifies the identity of a large, continuous body region.
  • C: In Artemia, multiple Hox genes are expressed together to define segments (e.g., swimmerets), whereas in grasshoppers, individual Hox genes define discrete segments.
  • D: Hox genes only control limb development in Artemia, but entire body segments in grasshoppers.

Explanation

Figure 21.20 and its caption explain that in Artemia, three Hox genes are expressed together in one region to specify swimmerets, while the fourth teal specifies genital segments. In the grasshopper, each Hox gene is expressed in a discrete region and specifies the identity of that region, illustrating a difference in their expression patterns leading to different body plans.