Correct option is C
Explanation:
Ubx expression levels in segments that give rise to wings/halteres:
- This suggests that differences in the quantity of Ubx protein could affect the development of these structures. However, it doesn’t fully explain the absence of halteres in four-winged insects like dragonflies, which do not possess any Ubx function in the haltere segment.
Ubx regulation at different developmental times in segments that give rise to wings/halteres:
- This refers to the timing of Ubx activation and its potential influence on wing and haltere formation. However, this option does not capture the primary difference between the two-winged and four-winged insects. The timing of Ubx regulation alone doesn’t explain the evolutionary difference in wing and haltere development.
Targets of Ubx in segments that give rise to wings/halteres:
- This is the correct answer. Ubx directly influences the development of specific structures by regulating downstream target genes. In Drosophila, Ubx is critical for suppressing wing formation in the haltere segment. In four-winged insects like dragonflies, the absence of Ubx function leads to the development of two pairs of wings instead of one pair of wings and one pair of halteres.
Ubx copy number and paralog evolution:
- While copy number variations and paralog evolution may play a role in some evolutionary scenarios, this option is less relevant to the immediate functional differences in wing and haltere development.
Conclusion:
The key difference between two-winged and four-winged insect species in relation to Ubx function lies primarily in how Ubx interacts with its target genes to influence wing and haltere development.
So, Option 3 (Targets of Ubx in segments that give rise to wings/halteres) is the correct answer. This option best explains how the Ubx gene influences wing and haltere differentiation by acting on its target genes, making it central to understanding the differences between two-winged and four-winged insects.
