Search results for "Microchromosome"

2020

Turtles, a speciose group consisting of more than 300 species, demonstrate karyotypes with diploid chromosome numbers ranging from 2n = 26 to 2n = 68. However, cytogenetic analyses have been conducted only to 1/3rd of the turtle species, often limited to conventional staining methods. In order to expand our knowledge of the karyotype evolution in turtles, we examined the topology of the (TTAGGG)n telomeric repeats and the rDNA loci by fluorescence in situ hybridization (FISH) on the karyotypes of two emydids: the Sicilian pond turtle, Emys trinacris, and the yellow-bellied slider, Trachemys scripta scripta (family Emydidae). Furthermore, AT-rich and GC-rich chromosome regions were detected …

Chicken orthologues of mammalian imprinted genes are clustered on macrochromosomes and replicate asynchronously.

2005

In the chicken genome, most orthologues of mouse imprinted genes are clustered on macrochromosomes. Only a few orthologues are located in the microchromosome complement. Macrochromosomal and, to a lesser extent, microchromosomal regions containing imprinted gene orthologues exhibit asynchronous DNA replication. We conclude that highly conserved arrays of imprinted gene orthologues were selected during vertebrate evolution, long before these genes were recruited for parent-specific gene expression by genomic imprinting mechanisms. Evidently, the macrochromosome complement provides a better chromatin environment for the establishment of asynchronous DNA replication and imprinted gene expressi…

Preparation and karyotype analysis of mitotic chromosomes of the freshwater sponge Spongilla lacustris.

1993

The present study documents for the first time the karyotype and mitotic chromosomes of a sponge. For the studies the freshwater sponge Spongilla lacustris (Lin. 1758) was used. Its karyotype comprises nine different chromosome pairs ranging in size from 2.1 to < or = 0.7 microns. Changes in size and shape of the chromosomes during the progression of mitosis are documented both light and electron microscopically. The data reveal that the lowest multicellular eukaryotes, the sponges, have already reached a high level of evolution of the mitotic mechanism.