Segmentation
Segmentation in biology means the division of some animal and plant bodies into a series of repeat sections or parts. It is common in some of the most successful groups of animals, such as arthropods, vertebrates and annelid worms.
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Segmentation of the body allows different regions of the body to develop for different uses.
Genes regulating development
changeWe now know a good deal about how the development of segmented animals is controlled. In a series of experiments with the fruit-fly Drosophila, E.B. Lewis was able to identify a complex of genes whose proteins bind to the regulatory regions of target genes. The latter then activate or repress cell processes which direct the final development of the organism.[1][2]
Furthermore, the sequence of these control genes show co-linearity: the order of the loci in the chromosome parallels the order in which the loci are expressed along the anterior-posterior axis of the body. Not only that, but this cluster of master control genes programs the development of all higher organisms.[3][4]
Each of the genes contains a homeobox, a remarkably conserved DNA sequence. This suggests the complex itself arose by gene duplication.[5][6][7]
In his Nobel lecture, Lewis said "Ultimately, comparisons of the [control complexes] throughout the animal kingdom should provide a picture of how the organisms, as well as the [control genes] have evolved".[8]
References
change- ↑ Lewis E.B. 1995. The bithorax complex: the first fifty years. Nobel Prize lecture. Repr. in Ringertz N. (ed) 1997. Nobel lectures, Physiology or Medicine. World Scientific, Singapore.
- ↑ Lawrence P. 1992. The making of a fly. Blackwell, Oxford.
- ↑ Duncan I. 1987. The bithorax complex. Ann. Rev. Genetics 21, 285–319.
- ↑ Lewis E.B. 1992. Clusters of master control genes regulate the development of higher organisms. J. Am. Medical Assoc. 267, 1524–1531.
- ↑ McGinnis W. et al. 1984. A conserved DNA sequence in homeotic genes of the Drosophila antennipedia and bithorax complexes. Nature 308, 428–433.
- ↑ Scott M.P. and Weiner A.J. 1984. Structural relationships among genes that control developmental sequence homology between the antennipedia, ultrabithorax and fushi tarazu loci of Drosophila. PNAS USA 81, 4115.
- ↑ Gehring W. 1999. Master control systems in development and evolution: the homeobox story. Yale.
- ↑ Duncan I. and G. Montgomery 2002. E.B. Lewis and the bithorax complex. Part I. Genetics 160: 1265–1272. PMC free article: [1] Duncan I. and G. Montgomery 2002. E.B. Lewis and the bithorax complex. Part II. Genetics 161: 1–10. PMC free article [2]