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Outline. Genetic Material Transformation DNA Structure Watson and Crick DNA Replication Prokaryotic versus Eukaryotic Replication Errors. Genetic Material. Frederick Griffith investigated virulence of Streptococcus pneumoniae - PowerPoint PPT Presentation
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DNA Structure & Function
Chapter 13
2DNA Structure DNA Structure & Function& Function
OutlineOutline
Genetic MaterialGenetic MaterialTransformationTransformation
DNA StructureDNA StructureWatson and CrickWatson and Crick
DNA ReplicationDNA ReplicationProkaryotic versus EukaryoticProkaryotic versus Eukaryotic
Replication ErrorsReplication Errors
3DNA Structure DNA Structure & Function& Function
Genetic MaterialGenetic Material
Frederick Griffith investigated virulence of Frederick Griffith investigated virulence of Streptococcus pneumoniaeStreptococcus pneumoniae Concluded that virulence passed from the Concluded that virulence passed from the dead strain to the living straindead strain to the living strain
TransformationTransformation
Further research by Avery et alFurther research by Avery et alDiscovered that DNA is the transforming Discovered that DNA is the transforming substancesubstance
DNA from dead cell was being incorporated DNA from dead cell was being incorporated into genome of living cellsinto genome of living cells
4Griffith’s Transformation Experiment
5DNA Structure DNA Structure & Function& Function
Reproduction of VirusesReproduction of Viruses
Viruses consist of a protein coat (capsid) Viruses consist of a protein coat (capsid) surrounding a nucleic acid coresurrounding a nucleic acid core
Bacteriophages are viruses that infect Bacteriophages are viruses that infect bacteriabacteria
Hershey and Chase:Hershey and Chase:Radioactively labeled the DNA core and Radioactively labeled the DNA core and protein capsid of a phageprotein capsid of a phage
Results indicated that DNA, not the protein, Results indicated that DNA, not the protein, enters the hostenters the host
The DNA of the phage contains genetic The DNA of the phage contains genetic information for producing new phagesinformation for producing new phages
6Bacteria and Bacteriophages
7Hershey and Chase Experiments
8DNA Structure DNA Structure & Function& Function
Structure of DNAStructure of DNA
DNA contains:DNA contains:Two Nucleotides with purine basesTwo Nucleotides with purine bases Adenine (A)Adenine (A) Guanine (G)Guanine (G)
Two Nucleotides with pyrimidine basesTwo Nucleotides with pyrimidine bases Thymine (T)Thymine (T) Cytosine (C)Cytosine (C)
9DNA Structure DNA Structure & Function& Function
Chargaff’s RulesChargaff’s RulesThe amounts of A, T, G, and C in DNA:The amounts of A, T, G, and C in DNA:
Identical in identical twinsIdentical in identical twinsVaries between individuals of a speciesVaries between individuals of a speciesVaries more from species to speciesVaries more from species to species
In each species, there are equal amounts of:In each species, there are equal amounts of:A & TA & TG & CG & C
All this suggests DNA uses complementary All this suggests DNA uses complementary base pairing to store genetic infobase pairing to store genetic info
Human chromosome estimated to contain, on Human chromosome estimated to contain, on average, 140 million base pairsaverage, 140 million base pairs
Number of possible nucleotide sequences Number of possible nucleotide sequences 4,140,000,0004,140,000,000
10Nucleotide Composition of DNA
11DNA Structure DNA Structure & Function& Function
Watson and Crick ModelWatson and Crick Model
Watson and Crick, 1953Watson and Crick, 1953
Constructed a model of DNAConstructed a model of DNA
Double-helix model is similar to a twisted Double-helix model is similar to a twisted ladderladder
Sugar-phosphate backbones make up the sidesSugar-phosphate backbones make up the sides
Hydrogen-bonded bases make up the rungsHydrogen-bonded bases make up the rungs
Received a Nobel Prize in 1962Received a Nobel Prize in 1962
12X-Ray Diffraction of DNA
13Watson/Crick Model of DNA
14DNA Structure DNA Structure & Function& FunctionReplication:Replication:
Prokaryotic vs. EukaryoticProkaryotic vs. Eukaryotic
Prokaryotic ReplicationProkaryotic Replication
Bacteria have a single circular loopBacteria have a single circular loop
Replication moves around the circular DNA Replication moves around the circular DNA molecule in both directionsmolecule in both directions
Produces two identical circlesProduces two identical circles
Cell divides between circles, as fast as every Cell divides between circles, as fast as every 20 minutes20 minutes
15DNA Structure DNA Structure & Function& FunctionReplication:Replication:
Prokaryotic vs. EukaryoticProkaryotic vs. EukaryoticEukaryotic ReplicationEukaryotic Replication
DNA replication begins at numerous points along DNA replication begins at numerous points along linear chromosomelinear chromosome
DNA Unwinds and unzips into two strandsDNA Unwinds and unzips into two strands Each old strand of DNA serves as a template for a Each old strand of DNA serves as a template for a
new strandnew strand Complementary base-pairing forms new strand on Complementary base-pairing forms new strand on
each old strandeach old strand Replication bubbles spread bi-directionally until they Replication bubbles spread bi-directionally until they
meetmeetSemiconservative:Semiconservative:
One original strand is conserved in each daughter One original strand is conserved in each daughter moleculemolecule
16Semiconservative Replication
of DNA
17Meselson and Stahl’sDNA replication experiment
18Replication:Prokaryotic vs.
Eukaryotic
19DNA Structure DNA Structure & Function& Function
Replication ErrorsReplication Errors
Genetic variations are the raw material for Genetic variations are the raw material for evolutionary changeevolutionary change
Mutation:Mutation:A permanent (but unplanned) change in base-A permanent (but unplanned) change in base-pair sequencepair sequence Some due to errors in DNA replicationSome due to errors in DNA replication
Others are due to to DNA damageOthers are due to to DNA damage
DNA repair enzymes are usually available to DNA repair enzymes are usually available to reverse most errorsreverse most errors
20DNA Structure DNA Structure & Function& Function
ReviewReview
Genetic MaterialGenetic MaterialTransformationTransformation
DNA StructureDNA StructureWatson and CrickWatson and Crick
DNA ReplicationDNA ReplicationProkaryotic versus EukaryoticProkaryotic versus Eukaryotic
Replication ErrorsReplication Errors
DNA Structure & Function
Ending Slide Chapter 13