Avian genomes: different karyotypes but a similar distribution of the GC-richest chromosome regions at interphase.
The chicken karyotype, like that of the vast majority of avian species, shows a large number of dot-shaped microchromosomes that are characterized, like most telomeric regions of the macrochromosomes, by the highest GC levels and the highest gene densities. In interphase nuclei, these gene-dense regions are centrally located, and are characterized by an open chromatin structure (a similar situation also exists in mammals). Avian species belonging to the Accipitridae family (diurnal raptors) show a karyotype with no very large chromosomes, and with only a very small number of microchromosomes. To identify the GC-rich (and gene-rich) regions of the chromosomes and nuclei from Accipitridae, we performed heterologous in-situ hybridizations using chicken GC-richest isochores as probes. Our results clearly show that the gene-rich regions are prevalently located in the few microchromosome pairs and in the telomeric regions of the middle-sized chromosomes, as well as in the interior of the interphase nuclei. This result is consistent with a common organization of the genome in the nuclei of warm-blooded vertebrates. Indeed, in spite of the different size and morphology of the chromosomes, the gene-dense regions are always located in the interior of the nuclei.
Federico
Concetta
C
Dipartimento di Biologia Animale M. La Greca, University of Catania, Italy.
Cantarella
Catia Daniela
CD
Scavo
Cinzia
C
Saccone
Salvatore
S
Bed'Hom
Bertrand
B
Bernardi
Giorgio
G
D000818:Animals; D002645:Chickens / Q000235:genetics*; D002875:Chromosomes / Q000648:ultrastructure; D020862:GC Rich Sequence; D016678:Genome; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D007399:Interphase / Q000235:genetics; D032085:Isochores / Q000235:genetics; D008677:Metaphase / Q000235:genetics; D020304:Raptors / Q000235:genetics*; D013045:Species Specificity
D032085:Isochores