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Jeremiah 10:12 12 He hath made the earth by his power, he hath established the world by his wisdom, and hath stretched out the heavens by his discretion. Replicons. Timothy G. Standish, Ph. D. The Information Catch-22. - PowerPoint PPT Presentation
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©2001 Timothy G. Standish
Jeremiah 10:12
12 He hath made the earth by his power, he hath established the world by his wisdom, and hath stretched out the heavens by his discretion.
©2001 Timothy G. Standish
RepliconsRepliconsTimothy G. Standish, Ph. D.
©2001 Timothy G. Standish
The Information Catch-22The Information Catch-22“With only poor copying fidelity, a primitive
system could carry little genetic information without L [the mutation rate] becoming unbearably large, and how a primitive system could then improve its fidelity and also evolve into a sexual system with crossover beggars the imagination.”
Hoyle F. 1987. "Mathematics of Evolution", Acorn Enterprises: Memphis TN, 1999, p 20
©2001 Timothy G. Standish
The Cell LifecycleThe Cell Lifecycle The cell lifecycle is well defined and can be
divided into four stages:– Gap 1 (G1) - The growth phase in which most cells
are found most of the time– Synthesis (S) - During which new DNA is synthesized– Gap 2 (G2) - No transcription or translation occurs
and final preparations for division are made– Mitosis - Cell division
Once Synthesis is initiated, the cell is committed to division
Thus initiation of DNA replication is a carefully controlled process in cells
©2001 Timothy G. Standish
G1
M
G2
S
The Cell LifecycleThe Cell LifecycleGap 1 - Doubling of cell size. Regular cellular activities. Transcription and translation etc.
Synthesis of DNA - Regular cell activities cease and a copy of all nuclear DNA is made
Gap 2 - Final preparation for division
Mitosis - Cell division
©2001 Timothy G. Standish
Stages of ReplicationStages of Replication Replication can be divided into three stages:1 Initiation - When DNA is initially split into two strands and
polymerization of new DNA is started2 Elongation - When DNA is polymerized3 Termination - When the new strands of DNA are completed
and some finishing touches may be put on the DNA Both elongation and termination may involve proof reading
of the DNA ensuring that mutations are not incorporated into newly formed DNA strands
©2001 Timothy G. Standish
InitiationInitiation Initiation starts at specific DNA sequences called origins
(Ori C = origin in E. coli chromosomes) Long linear chromosomes have many origins First the origin melts (splits into two single strands of
DNA) Next primers are added Finally DNA polymerase recognizes the primers and
starts to polymerize DNA 5’ to 3’ away from the primers
©2001 Timothy G. Standish
Initiation - Forming the Initiation - Forming the Replication Eye Or BubbleReplication Eye Or Bubble
3’ 5’
3’5’5’
5’
3’
3’
Origin of Replication
5’
3’
3’
5’
5’3’
5’
5’
5’
3’
3’3’
Replication eye orreplication bubble
©2001 Timothy G. Standish
Large Linear Chromosomes Have Large Linear Chromosomes Have Many Origins Of ReplicationMany Origins Of Replication
5’3’
3’5’
5’3’
3’5’
3’5’
5’3’
3’5’
5’3’
3’5’
5’3’
Origins of Replication
©2001 Timothy G. Standish
Cell Wall
CytoplasmCell Membrane
Bacteria Have Circular Bacteria Have Circular ChromosomesChromosomes
Termination ofReplication
Origin ofReplicationChromosome
©2001 Timothy G. Standish
ReplicationReplication
End of replicationTwo chromosomes
OriginalChromosome
Start of replicationTheta () structure
Replication goes in both directions
Mid replication
©2001 Timothy G. Standish
Binary Fission RevisitedBinary Fission Revisited
©2001 Timothy G. Standish
Various Replication StrategiesVarious Replication Strategies D-loop Rolling circle
©2001 Timothy G. Standish
F- bacteria
2 Conjugation2 ConjugationF plasmid
Mating Bridge
F+ bacteria
Fplasmid
©2001 Timothy G. Standish
2 Conjugation2 Conjugation
F- bacteria
F plasmid
F+ bacteria
Fplasmid
Mating Bridge
©2001 Timothy G. Standish
2 Conjugation2 Conjugation
F- bacteria
F plasmid
F+ bacteria
Fplasmid
Mating Bridge
©2001 Timothy G. Standish
2 Conjugation2 Conjugation
F- bacteria
F plasmid
F+ bacteria
Fplasmid
Mating Bridge
©2001 Timothy G. Standish
2 Conjugation2 Conjugation
F- bacteria
F plasmid
F+ bacteria
Fplasmid
Fplasmid
Mating Bridge
©2001 Timothy G. Standish
Transfer of genetic material
Hfr RecombinationHfr Recombination
F+ bacteria
F- bacteria
F plasmid Integration
Hfr cell
©2001 Timothy G. Standish
Hfr RecombinationHfr Recombination
F+ bacteria
F- bacteria
Crossing over Transfer of genetic material
Interruption of conjugation
Hfr cellF plasmid Integration
©2001 Timothy G. Standish
Hfr RecombinationHfr Recombination
F+ bacteria Hfr cellF plasmid Integration
F- bacteria
RecombinantBacteria
©2001 Timothy G. Standish