- What is the observed phenotype when the ultrabithorax gene is deleted in Drosophila?
(1) The third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings.
(2) Since it specifics the second thoracic segment, instead of antenna leg grows out of the head
socket.
(3) Since it specifies the third thoracic segment, a fly with two pairs of halters develop.
(4) Since this gene fails to be expressed in the second thoracic segment, the antennae sprout in the leg position. Learn about the effects of Ultrabithorax gene deletion in Drosophila, resulting in the transformation of the third thoracic segment into a second thoracic segment, causing flies to develop four wings.
The Ultrabithorax (Ubx) gene is a critical homeotic gene in Drosophila melanogaster that specifies the identity of the third thoracic segment (T3), where halteres normally develop. The gene encodes a transcription factor responsible for repressing wing development on T3 and promoting the formation of halteres, small balancing organs that are key to proper flight control in flies.
Phenotypic Consequences of Ubx Deletion
When the Ultrabithorax gene is deleted or functionally lost, the suppressive effect on wing development in T3 is lifted. As a result, the third thoracic segment undergoes a homeotic transformation where it adopts the identity characteristic of the second thoracic segment (T2). This leads to the development of an extra pair of wings in place of halteres, effectively resulting in flies with four wings instead of the usual two wings and two halteres.
Explanation of Alternative Options
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The Ubx gene does not specify the second thoracic segment; thus, statements describing Ubx effects on antennal or head structures are incorrect.
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The formation of two pairs of halteres does not occur upon Ubx loss; rather, halteres are transformed into wings.
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Expression or loss of Ubx does not cause antennae to sprout in leg positions.
Molecular Role of Ultrabithorax
Ubx functions at the molecular level by regulating multiple downstream target genes that control the development of wing and haltere tissues. It represses the expression of wing-specific genes such as Vestigial and Wingless in T3, ensuring that the segment develops haltere morphology.
Furthermore, Ubx interacts with chromatin remodeling complexes to maintain the repressed state of wing development genes, stabilizing segment-specific cell fates during development.
Conclusion
The deletion of the Ultrabithorax gene in Drosophila results in the third thoracic segment transforming into a second thoracic segment, producing an additional pair of wings and generating flies with four wings. This classical phenotype exemplifies the critical role of homeotic genes in maintaining segment identity and the morphological diversification of segments in animal development.
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15 Comments
Neelam Sharma
November 10, 2025The third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings
Kajal
November 12, 2025Option 1 is correct
Rishu
November 12, 2025The third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings is the right answer
priti khandal
November 12, 2025option 1st is correct
Bhawna Choudhary
November 13, 2025Option 1 is correct
Sonal Nagar
November 13, 2025Option 1st
Divya rani
November 13, 2025If ubx gene is deleted in drosophila, the third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings or two pair of wings.
Kirti Agarwal
November 13, 2025Opt 1
anjani sharma
November 13, 2025The third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings.
Neha Yadav
November 14, 2025The deletion of the Ultrabithorax gene in Drosophila results in the third thoracic segment transforming into a second thoracic segment, resulting in a fly with four wings.
Mohd juber Ali
November 15, 2025T3 convert into T2 a fly with four wings bcz in T3 ~pair of wings form except halters
Santosh Saini
November 16, 2025The third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings
Sakshi Kanwar
November 18, 2025The deletion of the Ultrabithorax gene in Drosophila results in the third thoracic segment transforming into a second thoracic segment, resulting in a fly with four wings.
Muskan Yadav
November 21, 2025The third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings.
Kavita Choudhary
November 21, 20251st is right
The third thoracic segment is transformed into another second thoracic segment resulting in a fly with four wings.