לוח שנה משולב

Globular Clusters (GCs) – tightly-bound spherical agglomerations of (as much as 10^6) stars – have long been regarded as being the ideal stellar laboratories, mainly owing to the fact that they constitute a “simple stellar population”. As such coeval/mono-metallic assemblies of stars, they have been extensively used for testing models of stellar evolution and population synthesis. This simple notion has, however, been shaken in recent years due to puzzling findings such as the presence of multiple stellar populations within single clusters. Lately, additional studies have emerged, which not only provide more evidence for the “non-simplicity” of the populations of GCs, but such that address with greater magnitude the question as for the possible origins/formation mechanisms. Can it ultimately be proven that a few, or maybe even a significant fraction, of the galactic GCs are indeed relics of the cores (the survived nuclei) of dwarf spheroidal galaxies, disrupted and dissolved within the Milky Way?

Evolution maintains organismal fitness by preserving genomic
information. This is widely assumed to involve conservation of
specific genomic loci among species. Many genomic encodings are now
recognized to integrate small contributions from multiple genomic
positions into quantitative dispersed codes, but the evolutionary
dynamics of such codes are still poorly understood. We show that in
yeast, sequences that quantitatively affect packaging of DNA into
nucleosomes evolve under compensatory dynamics that maintain near
optimal sequences through spatially coupled harmful and beneficial
substitutions. Evolutionary modeling combined with data on yeast
polymorphisms support the idea that these dynamics are a consequence
of weak selection. Our results imply that maintenance of molecular
function may be coupled to rapid sequence divergence rather than
conservation. We suggest that compensatory dynamics is an inevitable
consequence of the conservation of quantitative genomic encodings,
with a major role in the evolution of genomes.


I'll present ideas, challenges and models from a relatively general
perspective, without assuming much knowledge of biology. If time will
permit, I'll also show some new data on the 3D organization of
chromosomes and discuss emerging questions on the regulation of
chromosomes function and dynamics.