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This is an old revision of this page, as edited by Celefin (talk | contribs) at 19:03, 13 April 2009 (more pair-rule). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
Expression of the pair-rule genes even-skipped and fushi tarazu in alternating bands in the Drosophila early embryo. Each band corresponds to one parasegment.

A pair-rule gene is a type of gene involved in the development of the segmented embryos of insects. Pair-rule genes are defined by the effect of a mutation in that gene, which causes the loss of the normal developmental pattern in alternating segments.

Pair-rule genes were first described by Christiane Nusslein-Volhard and Eric Wieschaus in 1980.[1] They used a genetic screen to identify genes required for embryonic development in the fruit fly Drosophila melanogaster. In normal unmutated Drosophila, each segment produces bristles called denticles in a band arranged on the side of the segment closer to the head (the anterior). They found five genes – even-skipped, hairy, odd-skipped, paired and runt – where mutations caused the deletion of a particular region of every alternate segment. For example, in even-skipped, the denticle bands of alternate segments are missing, which results in an embryo having half the number of denticle bands. Later work identified more pair-rule genes in the Drosophile early embryo – fushi tarazu, odd-paired, sloppy paired, and tenm.[2][3]

Once the pair-rule genes had been identified at the molecular level it was found that each gene is expressed in alternate parasegments – regions in the embryo that are closely related to segments, but are slightly out of register. Each parasegment includes the posterior part of one (future) segment, and an anterior part of the next (more posterior) segment


gap gene is expressed in a band in the early embyro generally correlated with the region that is absent in the mutant.[4][5] In Drosophila the gap genes encode transcription factors, and they directly control the expression of another set of genes involved in segmentation, the pair-rule genes. The gap genes themselves are expressed under the control of maternal effect genes such as bicoid and nanos, and regulate each other to achieve their precise expression patterns.

  1. ^ Nüsslein-Volhard C, Wieschaus E (1980). "Mutations affecting segment number and polarity in Drosophila". Nature. 287 (5785): 795–801. PMID 6776413. {{cite journal}}: Unknown parameter |month= ignored (help)
  2. ^ Wakimoto BT, Kaufman TC (1981). "Analysis of larval segmentation in lethal genotypes associated with the antennapedia gene complex in Drosophila melanogaster". Dev. Biol. 81 (1): 51–64. PMID 6780397. {{cite journal}}: Unknown parameter |month= ignored (help)
  3. ^ Baumgartner S, Martin D, Hagios C, Chiquet-Ehrismann R (1994). "Tenm, a Drosophila gene related to tenascin, is a new pair-rule gene". EMBO J. 13 (16): 3728–40. PMC 395283. PMID 8070401. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  4. ^ Knipple DC, Seifert E, Rosenberg UB, Preiss A, Jäckle H (1985). "Spatial and temporal patterns of Krüppel gene expression in early Drosophila embryos". Nature. 317 (6032): 40–4. PMID 2412131.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ Bender M, Horikami S, Cribbs D, Kaufman TC (1988). "Identification and expression of the gap segmentation gene hunchback in Drosophila melanogaster". Dev. Genet. 9 (6): 715–32. doi:10.1002/dvg.1020090604. PMID 2849517.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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