[Campbell Biology P.829] In some plant species, sepals resemble petals, and both are collect... | Practice Question

In some plant species, sepals resemble petals, and both are collectively called 'tepals.' Based on the ABC hypothesis, which genetic alteration would most likely account for the development of tepals?

  • A: Suppression of A gene activity in the first whorl
  • B: Extension of B gene activity into the first whorl
  • C: Suppression of C gene activity throughout the flower
  • D: Extension of C gene activity into the second whorl

Explanation

Tepals signify that both the outermost normally sepals and second petals whorls display petal identity. According to the ABC hypothesis, petals develop when both A and B genes are expressed. If B gene activity extends into the first whorl where A genes are already active , then both the first and second whorls would express A and B genes, resulting in petal-like structures tepals in both positions.