Book of Abstracts: Albany 2009
June 16-20 2009
© Adenine Press (2008)
Individualization of Chromatids in Higher Eukaryotes
Coordination between eukaryotic origins of replication (ORIs) is not understood. ORIs are not defined by sequence; however, unspecified structural mechanism of their definition is indicated. The temporal aspects of ORIs coordination were studied and it was shown that chromatin, depending on its structural status, replicate at different times. However, the mechanism of spatial separation of the replication's products, particularly the problem of avoiding mixing between sister chromatids, remains unexplained.
There is strong evolutionary pressure resulting in semi-conservative replication as indicated by extremely low level of sister chromatid exchange errors(SCE). The reason for such strong evolutionary pressure is not obvious, but it indicates that the DNA strands are differentiated from each other along the whole length of the chromsome. Observations of diplochromosomes show that this mechanism is not based on sequence but rather on epigenetic memory of generation when each of the strands in the DNA duplex was synthesized.
The plausible mechanism explaining this phenomenon is based on formation of asymmetric hemicatenene during DNA synthesis. The details of the mechanism as well as its possible involvement in other aspects of chromatin organization and epigenetic memory will be discussed.