Molecular Biology 分子生物学课件
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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-T rich
E. coli
Origin
oriC, 245 bp Bidirectional Circular replication
Termination
ter Short sequence ~23 bp, functions in one direction Requires the product of tus gene, which
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
Create an artificial chromosome: the first step
The DNA constituting an origin can be isolated by its ability to support replication of any DNA sequence to which it is joined
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 origin Origins in eukaryotes do not function in segregation, but are concerned only with replication
DNA from the origin can be cloned into a molecule that lacks origin, this will create a plasmid capable of autonomous replication
Origins have been identified in bacteria, yeast, chloroplasts, mitochondria, but not in higher eukaryotes
Molecular Biology: DNA
Jun Yang, Ph. D. Office: Bldg 3, Room 601 Tel: 8721 7149 Office hour: Tuesdays, 2-3 pm or
by appointment
Replicon
The unit of DNA in which an individual act of replication occurs
q-structure
When a replicon is circular, the presence of an eye forms the θ-structure
The successive stages of replication of the circular DNA of polyoma virus are visualized by electron microscopy
recognizes the consensus sequence and prevents the replication fork from proceeding
Termination in E. coli
Two termination regions, each contains multiple terminators. And each is specific for one direction of fork movement. “Replication fork trap”
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
A genome in a prokaryotic cell is a single repliBaidu Nhomakorabeaon: 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
Control elements: origin, terminus
Regulation: cis-acting Origin site, trans-acting regulator protein (coded within the replicon, or somewhere else)
A-T rich
E. coli
Origin
oriC, 245 bp Bidirectional Circular replication
Termination
ter Short sequence ~23 bp, functions in one direction Requires the product of tus gene, which
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
Create an artificial chromosome: the first step
The DNA constituting an origin can be isolated by its ability to support replication of any DNA sequence to which it is joined
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 origin Origins in eukaryotes do not function in segregation, but are concerned only with replication
DNA from the origin can be cloned into a molecule that lacks origin, this will create a plasmid capable of autonomous replication
Origins have been identified in bacteria, yeast, chloroplasts, mitochondria, but not in higher eukaryotes
Molecular Biology: DNA
Jun Yang, Ph. D. Office: Bldg 3, Room 601 Tel: 8721 7149 Office hour: Tuesdays, 2-3 pm or
by appointment
Replicon
The unit of DNA in which an individual act of replication occurs
q-structure
When a replicon is circular, the presence of an eye forms the θ-structure
The successive stages of replication of the circular DNA of polyoma virus are visualized by electron microscopy
recognizes the consensus sequence and prevents the replication fork from proceeding
Termination in E. coli
Two termination regions, each contains multiple terminators. And each is specific for one direction of fork movement. “Replication fork trap”
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
A genome in a prokaryotic cell is a single repliBaidu Nhomakorabeaon: 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