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Foothill High School Science DepartmentFoothill High School Science Department
DNA & RNADNA & RNA
DNADNA
Foothill High School Science DepartmentFoothill High School Science Department
Griffith & TransformationGriffith & Transformation
• 1928• Studying Natural Bacterial
Pneumonia caused by:– Streptococcus pneumoniae• Smooth (pathogenic)• Rough (non-pathogenic)
S. pneumonia in sputumNotice capsule
Gram Positive Diplococci
Foothill High School Science DepartmentFoothill High School Science Department
Streptococcus pneumoniaStreptococcus pneumonia
OptochinDisc
Type 3VERY Mucoid
Foothill High School Science DepartmentFoothill High School Science Department
Griffith’s ExperimentsGriffith’s Experiments
• Injected Mice–Smooth – Mice Died–Rough – Mice Didn’t Get Sick
–Heat Killed Smooth Heat Killed Smooth – Mice Didn’t Get Sick• Illness Not Caused By Poison
Foothill High School Science DepartmentFoothill High School Science Department
TransformationTransformation
Mixed Heat Killed Smooth With Mixed Heat Killed Smooth With Rough Live Bacteria.Rough Live Bacteria.
–Mice DiedMice Died
–Autopsy Revealed Lungs Full Of Smooth Strain of Bacteria
HOW?? Rough Bacteria Don’t Kill!HOW?? Rough Bacteria Don’t Kill!
Foothill High School Science DepartmentFoothill High School Science Department
Griffiths TransformationGriffiths Transformation
Foothill High School Science DepartmentFoothill High School Science Department
TransformationTransformation
• Heat Killed Smooth Bacteria– Still Contained The Information On How To
Become Smooth–And Could Transmit That Info–And Transform Rough Bacteria To The
Smooth (Pathogenic) Form
Foothill High School Science DepartmentFoothill High School Science Department
Avery & DNAAvery & DNA
• 1944• Repeated Griffith’s Work• Then Did Experiments to
Find Out What Was Transforming the Bacteria
• By Treating The Extract From Heat Killed Smooth Bacteria To Destroy Specific Types Of Compounds
Foothill High School Science DepartmentFoothill High School Science Department
Avery & DNAAvery & DNA
Treated Extract To DestroyProteinsProteins
LipidsLipidsCarbohydratesCarbohydrates
RNARNATransformation Still OccurredTransformation Still Occurred
Foothill High School Science DepartmentFoothill High School Science Department
Avery & DNAAvery & DNA
Then They Treated The Extract & Then They Treated The Extract & Destroyed The DNADestroyed The DNA
Transformation DidTransformation Did NOTNOT Occur Occur
DNA Was The Transforming FactorDNA Was The Transforming Factor
Foothill High School Science DepartmentFoothill High School Science Department
Avery & DNAAvery & DNA
Key ConceptAvery and other scientists discovered Avery and other scientists discovered
that DNA stores and transmits the that DNA stores and transmits the genetic information from one genetic information from one generation of an organism to the next generation of an organism to the next generationgeneration..
Foothill High School Science DepartmentFoothill High School Science Department
The Structure of DNAThe Structure of DNA
Chargaffs RulesChargaffs Rules–Discovered That Certain Nucleotides
Were Always Present In The Same Percentages:– AdenineAdenine & ThymineThymine–GuanineGuanine & CytosineCytosine–% In Each Species Different–Nobody Knew Why
Foothill High School Science DepartmentFoothill High School Science Department
Hershey-Chase ExperimentHershey-Chase Experiment
• 19521952• Studied Virus Particles, Studied Virus Particles,
Especially Especially BacteriophagesBacteriophages
Martha Chase & Alfred Hershey
Foothill High School Science DepartmentFoothill High School Science Department
Hershey-Chase ExperimentHershey-Chase Experiment
• Bacteriophages– Composed of DNA or RNA– and a Protein Coat
– Figured Whichever Part Entered The Bacteria – Carried The Genes
• Used Radioactive Markers
Foothill High School Science DepartmentFoothill High School Science Department
Radioactive MarkersRadioactive Markers
• Grew Viruses In Cultures ContainingGrew Viruses In Cultures Containing– Radioactive Phosphorus ( Radioactive Phosphorus ( 3232P )P )
andand
– Radioactive Sulfur ( Radioactive Sulfur ( 3535S )S )
Proteins Contain Proteins Contain NoNo Phosphorous PhosphorousDNA Contains DNA Contains NoNo Sulfur Sulfur
Foothill High School Science DepartmentFoothill High School Science Department
Radioactive MarkersRadioactive Markers
Therefore:Therefore:IfIf The Interior Of The Bacteria Contained The Interior Of The Bacteria Contained::
( ( 3232P ) Then DNA Contained GenesP ) Then DNA Contained Genes( ( 3535S ) Then Protein Contained GenesS ) Then Protein Contained Genes
Nearly All The Bacteria ContainedNearly All The Bacteria Contained( ( 3232PP ) )
Therefore Therefore DNA Contained GenesDNA Contained Genes
Foothill High School Science DepartmentFoothill High School Science Department
Hershey-ChaseHershey-Chase
Bacteriophage(virus that infects bacteria)
Outer, Protein CoatContains Sulfur – No Phosphorus
E. coli bacteria(infected by Bacteriophage)
Bacteriophage DNA injected into the E. coli
Bacteriophage DNA contains Phosphorous but NO Sulfur
Foothill High School Science DepartmentFoothill High School Science Department
Hershey-ChaseHershey-Chase
Foothill High School Science DepartmentFoothill High School Science Department
Hershey - ChaseHershey - Chase
Key Concept:Hershey and Chase concluded that
the genetic material of the bacteriophage was:
DNA, not Protein.DNA, not Protein.
Foothill High School Science DepartmentFoothill High School Science Department
The Structure of DNAThe Structure of DNA
• X-Ray Diffraction– Early 1950’s–Rosalind Franklin–Doesn’t Show Structure
But Provides Clues• DNA Twisted In Coils• Two Strands• Nitrogenous Base In
Center
Foothill High School Science DepartmentFoothill High School Science Department
Photo 51Photo 51
Foothill High School Science DepartmentFoothill High School Science Department
• Watson & CrickWatson & Crick– Building 3Building 3
Dimensional ModelsDimensional Models– 1953 Saw Franklins1953 Saw Franklins
X-ray WorkX-ray Work– Immediately Recognized Immediately Recognized
What The Structure Had What The Structure Had To Be:To Be:
A Double Helix
The Double HelixThe Double Helix
Foothill High School Science DepartmentFoothill High School Science Department
The Structure of DNAThe Structure of DNA
• Scientists still didn’t know:Scientists still didn’t know:–How information was carried between How information was carried between
generationsgenerations–How genes were structuredHow genes were structured–How genes were copiedHow genes were copied
Foothill High School Science DepartmentFoothill High School Science Department
The Structure of DNAThe Structure of DNA• DNA is a long Molecule of DNA is a long Molecule of
repeating nucleotidesrepeating nucleotides• Each nucleotide has 3 Each nucleotide has 3
parts:parts:– 5 Carbon Sugar 5 Carbon Sugar
(Deoxyribose)(Deoxyribose)– 1 Phosphate Group1 Phosphate Group– 1 Nitrogenous Base1 Nitrogenous Base
Foothill High School Science DepartmentFoothill High School Science Department
The Structure of DNAThe Structure of DNA
• There are 4 Nitrogenous Bases 4 Nitrogenous Bases in DNA• The 4 Bases are two types:– PurinesPurines which are Double Ring Molecules
• Adenine• Guanine
– PyrimidinesPyrimidines which are Single Ring Molecules
• Cytosine• Thymine
Foothill High School Science DepartmentFoothill High School Science Department
Purines PyrimidinesPurines Pyrimidines
Foothill High School Science DepartmentFoothill High School Science Department
Watson & CrickWatson & Crick
Key ConceptKey Concept::Watson & Crick’s Model of DNA Watson & Crick’s Model of DNA
was a Double Helix, was a Double Helix,
in which Two (2) Strands were in which Two (2) Strands were wound around each other.wound around each other.
Foothill High School Science DepartmentFoothill High School Science Department
The Structure of DNAThe Structure of DNA
Nitrogenous BasesNitrogenous BasesForms Rungs of DNA LadderForms Rungs of DNA Ladder
Phosphate/DeoxyribosePhosphate/DeoxyriboseForm Sides of the DNA Form Sides of the DNA
LadderLadder
Foothill High School Science DepartmentFoothill High School Science Department
Watson & CrickWatson & Crick
• Discovered The Double Helix• Held Together By Hydrogen Bonds
Between The Nitrogenous Bases• Base Pairing
A:TA:T and G:CG:CExplained Chargaff’s Rule
Foothill High School Science DepartmentFoothill High School Science Department
Double HelixDouble Helix