Compositional mapping of chicken chromosomes and identification of the gene-richest regions

What is it about?

The assessment of the GC level of chromosomal bands led to the identification, in the human chromosomes, of the GC-richest and of the GC-poorest isochores. The compositional distribution of avian isochores is very similar to that of most mammals, the only significant difference being the presence of an additional, GC-richest, isochore family. In contrast, the avian karyotypes are very different from those of mammals, being characterized, in most species, by few macrochromosomes and by a large number of microchromosomes. The ‘compositional mapping’ of chicken mitotic and meiotic chromosomes by in-situ hybridization of isochore families showed that the chicken GC-richest isochores are localized not only on a large number of microchromosomes, but also on almost all telomeric bands of macrochromosomes. On the other hand, the GC-poorest isochores are generally localized on the internal regions of macrochromosomes and are almost absent in microchromosomes.

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Why is it important?

The distinct localization of the GC-richest and the GC-poorest bands observed on human chromosomes appears to be a general feature of chromosomes from warm-blooded vertebrates.

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