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.
![Thumb](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Harpaphe_haydeniana_002.jpg/640px-Harpaphe_haydeniana_002.jpg)
![Thumb](http://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Gray_111_-_Vertebral_column.png/125px-Gray_111_-_Vertebral_column.png)
Segmentation of the body allows different regions of the body to develop for different uses.
Genes regulating development
We 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
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