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Yale > Molecular Cellular and Developmental Biology > Graduate Program (919 words) |
 | Somites are the segmented precursors to the vertebral column and skeletal muscle within the trunk and tail of vertebrate embryos. |
| In the anterior of this field of somite precursor cells, the stripes of gene expression are stabilized and ultimately determine the position of the next segment border. |
| Different regions of the anterior/posterior axis require distinct genes to establish the somitic pattern: the Notch pathway mutations, in mouse, zebrafish and humans, mostly affect the posterior somites while the anterior somites are normal. |
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Metamerism - LoveToKnow 1911 (2594 words) |
| The sixth by the blood-vessels of the somite; the seventh by the bit of alimentary tract which traverses it; and the eighth by the neuromere (nerve ganglion pair, commissures, connectives and nerve branches). |
| The praegenital somite of the Arachnida is an example of a somite which is preserved in some members of the group and partially or entirely excalated in other cases, sometimes with fusion of its remnants to neighbouring somites. |
| Thus, a case of fusion of partially atrophied somites may simulate the appearance of incipient merogenesis or formation of new somites, and, vice versa, incipient merogenesis may be misinterpreted as a case of fusion of once separate and fully-formed somites. |
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