[小学教育]浙江大学生物化学与分子生物学笔记Molecular Biology杨军.ppt

Molecular Biology:DNA Jun Yang, Ph. D. Office: Bldg 3, Room 601 Tel: 8721 7149 Office hour: Tuesdays, 2-3 pm or by appointment The structure of this section Part I. Replication The replicon DNA replication Recombination and repair Part II. Moving elements Transposons Retrovirus and retroposons Rearrangement of DNA Replicon The link between replication and cell cycle: The entire genome must be replicated precisely once for every cell division Initiation of DNA replication commits the cell to a further division If replication proceeds, the consequent division cannot be permitted to occur until the replication event completed Replicon The unit of DNA in which an individual act of replication occurs Each replicon “fires” once and only once in each cell cycle Control elements: origin, terminus Regulation: cis-acting Origin site, trans-acting regulator protein (coded within the replicon, or somewhere else) A genome in a prokaryotic cell is a single replicon: single copy control Plasmid constitutes a separate replicon may replicate with the bacterial genome under single copy control; or, under multicopy control (more copies of plasmid than the bacterial chromosome) Quite the contrary, Each eukaryotic chromosome contains a large number of replicons may not be active simultaneously, but cannot be activated more than once in the cell cycle Define the origins The “eye” Replication fork The point at which replication is occurring: unidirectional or bidirectional q-structure When a replicon is circular, the presence of an eye forms the θ-structure The bacterial genome is a single circular replicon A bacterial replicon should be able to: Initiate a replication cycle Control the frequency of initiation events Segregate replicated chromosomes to daughter cells The first two functions are properties of the origin Segregation could be an independent function, but in prokaryotic systems it is usually determined by sequences in the vicinity of the orig