A pair-rule gene is a type of gene involved in the development of the segmented embryos of insects. Pair-rule genes are expressed as a result of differing concentrations of gap gene proteins, which encode transcription factors controlling pair-rule gene expression. 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 Nüsslein-Volhard and Eric Wieschaus in 1980. 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 Drosophila early embryo – fushi tarazu, odd-paired and sloppy paired.
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. The bands of expression of the pair-rule genes correspond to the regions missing in the mutant. The expression of the pair-rule genes in bands is dependent both upon direct regulation by the gap genes and on regulatory interactions between the pair-rule genes themselves.
- Gilbert, SF (2000). Developmental Biology (6th ed.). Sunderland (MA): Sinauer Associates. pp. The Origins of Anterior–Posterior Polarity. Retrieved 23 October 2015.
- "Segmentation Genes in Drosophila Development: Pair Rule, Segment Polarity & Gap Genes". Study.com. Retrieved 23 October 2015.
- Nüsslein-Volhard C, Wieschaus E (October 1980). "Mutations affecting segment number and polarity in Drosophila". Nature. 287 (5785): 795–801. doi:10.1038/287795a0. PMID 6776413.
- Wakimoto BT, Kaufman TC (January 1981). "Analysis of larval segmentation in lethal genotypes associated with the antennapedia gene complex in Drosophila melanogaster". Dev. Biol. 81 (1): 51–64. doi:10.1016/0012-1606(81)90347-X. PMID 6780397.
- Hafen E, Kuroiwa A, Gehring WJ (July 1984). "Spatial distribution of transcripts from the segmentation gene fushi tarazu during Drosophila embryonic development". Cell. 37 (3): 833–41. doi:10.1016/0092-8674(84)90418-5. PMID 6430568.
- Ingham, P. W.; K. R. Howard & D. Ish-Horowicz (1985). "Transcription pattern of the Drosophila segmentation gene hairy". Nature. 318: 439–445. doi:10.1038/318439a0.
- Macdonald PM, Ingham P, Struhl G (December 1986). "Isolation, structure, and expression of even-skipped: a second pair-rule gene of Drosophila containing a homeo box". Cell. 47 (5): 721–34. doi:10.1016/0092-8674(86)90515-5. PMID 2877745.
- Lawrence PA, Johnston P, Macdonald P, Struhl G (1987). "Borders of parasegments in Drosophila embryos are delimited by the fushi tarazu and even-skipped genes". Nature. 328 (6129): 440–2. doi:10.1038/328440a0. PMID 2886916.
- Ingham, P. W.; Ish-Horowicz, D. & Howard, KR (1986). "Correlative changes in homoeotic and segmentation gene expression in Krüppel mutant embryos of Drosophila". The EMBO Journal. 5 (7): 1659.
- Howard K . & Ingham P. "Regulatory interactions between the segmentation genes fushi tarazu, hairy, and engrailed in the Drosophila blastoderm". Cell. 44 (6): 949–957. doi:10.1016/0092-8674(86)90018-8.
- The Interactive Fly: http://www.sdbonline.org/fly/aignfam/gapnprl.htm