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Unformatted text preview: We still do not know why the insect genes are clus- tered or organized in this colinear fashion, but, regard- less of the roles of these features, the same structural or- ganization—clustering and colinearity—is seen for the equivalent genes in mammals, which are organized into the Hox clusters (see Figure 18-30a). The major differ- ence between flies and mammals is that there is only one HOM-C cluster in the insect genome, whereas there are four Hox clusters, each located on a different chro- mosome, in mammals. These four Hox clusters are paral- ogous, meaning that the order of genes in each cluster is very similar, as if the entire cluster had been quadrupli- cated in the course of vertebrate evolution. Each of the genes near the left end of each Hox cluster is quite sim- ilar not only to the others, but also to one of the insect HOM-C genes at the left end of the cluster. Similar relations hold throughout the clusters. Finally, and most notably, the Hox genes are expressed so as to define...
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.
- Spring '08