Editing Halteres (section)

==Genetics==

In segmented organisms there are genes called [[Hox gene]]s, which determine the development of [[serial homology|serial homologs]], or repeating structures within an organism (e.g. jointed appendages of [[arthropod]]s or [[vertebra]]e in mammals<ref>{{cite web|title=Serial homology|url=http://www.britannica.com/science/serial-homology|website=britannica.com/|publisher=Encyclopædia Britannica, inc.|access-date=16 November 2015}}</ref>). In insects, the [[thorax]] is separated into different segments. One of the things that the Hox gene [[ultrabithorax|''Ultrabithorax (Ubx)'']] is responsible for, is specifying the identity of the third [[thorax|thoracic]] segment of their body.<ref name="Hersh 2007">{{cite journal|last1=Hersh|first1=Bradley M.|last2=Nelson|first2=Craig E.|last3=Stoll|first3=Samantha J.|last4=Norton|first4=Jason E.|last5=Albert|first5=Thomas J.|last6=Carroll|first6=Sean B.|title=The UBX-regulated network in the haltere imaginal disc of D. melanogaster|journal=Developmental Biology|date=February 2007|volume=302|issue=2|pages=717–727|doi=10.1016/j.ydbio.2006.11.011|pmid=17174297|pmc=1892158}}</ref> Proper hindwing development in a number of insect species is dependent on ''Ubx'', including butterflies, beetles, and flies.<ref name="Weatherbee 1998">{{cite journal|last1=Weatherbee|first1=SD|last2=Halder|first2=G|last3=Kim|first3=J|last4=Hudson|first4=A|last5=Carroll|first5=S|title=Ultrabithorax regulates genes at several levels of the wing-patterning hierarchy to shape the development of the Drosophila haltere |journal=Genes & Development|date=15 May 1998|volume=12|issue=10|pages=1474–82|pmid=9585507|doi=10.1101/gad.12.10.1474|pmc=316835}}</ref><ref>{{cite journal|last1=Weatherbee|first1=SD|last2=Nijhout|first2=HF|last3=Grunert|first3=LW|last4=Halder|first4=G|last5=Galant|first5=R|last6=Selegue|first6=J|last7=Carroll|first7=S|title=Ultrabithorax function in butterfly wings and the evolution of insect wing patterns |journal=Current Biology|date=11 February 1999|volume=9|issue=3|pages=109–15|pmid=10021383|doi=10.1016/s0960-9822(99)80064-5|s2cid=15385556|doi-access=free|bibcode=1999CBio....9..109W }}</ref><ref>{{cite journal|last1=Tomoyasu|first1=Y|last2=Wheeler|first2=SR|last3=Denell|first3=RE|title=Ultrabithorax is required for membranous wing identity in the beetle Tribolium castaneum |journal=Nature|date=10 February 2005|volume=433|issue=7026|pages=643–7|pmid=15703749|doi=10.1038/nature03272|bibcode=2005Natur.433..643T|s2cid=4336906}}</ref> In fruit flies, (''Ubx'') is responsible for the formation of the halteres during [[metamorphosis]]. If this gene is experimentally deactivated, the haltere will develop into a fully formed wing.<ref name="Hersh 2007" /> This single [[homeotic gene]] change results in a radically different [[phenotype]], but also begins to give us some insight into how the ancestors of flies' hindwings may have originally evolved into halteres.<ref name="Hersh 2007" />

Though it is clear that ''Ubx'' is the primary gene responsible for hindwing formation, Ubx also regulates other genes once expressed. Weatherbee (1998) postulated that differences in ''Ubx'' expression patterns or levels may not be responsible for the observed physiological changes. Instead, he suggested that ''Ubx''-regulated target gene sets were the direct source of the observed changes. Several ''Ubx''-regulated target genes have been identified, including two direct targets, ''spalt'' and ''knot'', which are expressed in the wing and repressed in halteres, and which are not affected by [[extradenticle]].<ref>{{cite journal|last1=Hersh|first1=BM|last2=Carroll|first2=SB|title=Direct regulation of knot gene expression by Ultrabithorax and the evolution of cis-regulatory elements in Drosophila |journal=Development |date=April 2005|volume=132|issue=7|pages=1567–77|pmid=15753212|doi=10.1242/dev.01737|doi-access=free}}</ref><ref>{{cite journal|last1=Galant|first1=R|last2=Walsh|first2=CM|last3=Carroll|first3=SB|title=Hox repression of a target gene: extradenticle-independent, additive action through multiple monomer binding sites |journal=Development |date=July 2002|volume=129|issue=13|pages=3115–26|doi=10.1242/dev.129.13.3115|pmid=12070087}}</ref> Other genes which are expressed in wings and repressed in halteres have also been identified, but whether or not they act as direct targets of ''Ubx'' regulation are still unknown.<ref name="Weatherbee 1998" /><ref>{{cite journal|last1=Crickmore|first1=MA|last2=Mann|first2=RS|title=Hox control of organ size by regulation of morphogen production and mobility |journal=Science|date=7 July 2006|volume=313|issue=5783|pages=63–8|pmid=16741075|doi=10.1126/science.1128650|pmc=2628481|bibcode=2006Sci...313...63C}}</ref><ref>{{cite journal|last1=Mohit|first1=P|last2=Makhijani|first2=K|last3=Madhavi|first3=MB|last4=Bharathi|first4=V|last5=Lal|first5=A|last6=Sirdesai|first6=G|last7=Reddy|first7=VR|last8=Ramesh|first8=P|last9=Kannan|first9=R|last10=Dhawan|first10=J|last11=Shashidhara|first11=LS|title=Modulation of AP and DV signaling pathways by the homeotic gene Ultrabithorax during haltere development in Drosophila |journal=Developmental Biology|date=15 March 2006|volume=291|issue=2|pages=356–67|pmid=16414040|doi=10.1016/j.ydbio.2005.12.022|doi-access=free}}</ref>