June 12th, 2006

homuncul

БИОЛОГИЯ

перестройка генома своими силами....


Annual Review of Microbiology (2002)
Genome Remodeling in Ciliated Protozoa
The germline genomes of ciliated protozoa are dynamic structures, undergoing massive DNA rearrangement during the formation of a functional macronucleus. Macronuclear development involves chromosome fragmentation coupled with de novo telomere synthesis, numerous DNA splicing events that remove internal segments of DNA, and, in some ciliates, the reordering of scrambled gene segments. Despite the fact that all ciliates share similar forms of DNA rearrangement, there appears to be great diversity in both the nature of the rearranged DNA and the molecular mechanisms involved. Epigenetic effects on rearrangement have also been observed, and recent work suggests that chromatin differentiation plays a role in specifying DNA segments either for rearrangement or for elimination.


J. Exp. Zool. (Mol. Dev. Evol.), 2005.
Evolution of developmentally regulated genome rearrangements in eukaryotes
Developmentally regulated genome rearrangements (DRGR) - processes that alter genomes either in specific cells or during specific life cycle stages - are widespread throughout eukaryotes. This contrasts with the view that genome structure and content remain essentially constant throughout an organism's life cycle. Here we review three categories of developmentally regulated genome processing in eukaryotes: genome-wide rearrangements, targeted rearrangements, and a special case of amplification of ribosomal DNA genes. Mapping these types of DRGR onto eukaryotic phylogeny indicates that each type of processing is found in multiple independent lineages. We propose that such genome rearrangements were present within the last common ancestor of extant eukaryotes, and that future research will yield evidence of homologous epigenetic mechanisms underlying genome processing among diverse eukaryotes.


см. также
http://nature-wonder.livejournal.com/15861.html