DNADNAOROR

Why you look like your Why you look like your parents!!parents!!

Frederick GriffithFrederick Griffith

Experiment by GriffithExperiment by Griffith

See page 288 in your bookSee page 288 in your book Smooth is a pathogenSmooth is a pathogen Rough is harmlessRough is harmless Heat killed pathogen mixed with live Heat killed pathogen mixed with live

harmless bacteria caused mice to dieharmless bacteria caused mice to die—why?—why?

Think about what happens in your Think about what happens in your body!!! Think about “bird flu”!!!!body!!! Think about “bird flu”!!!!

““Transformation”Transformation”

Oswald AveryOswald Avery

Experiment from AveryExperiment from Avery Created a “juice” from the heat-killed Created a “juice” from the heat-killed

bacteria of Griffith.bacteria of Griffith. Treated the juice with different Treated the juice with different

enzymes that would destroy one type enzymes that would destroy one type of molecule at a time.of molecule at a time.

Injected mice—the juice that was Injected mice—the juice that was treated with DNA destroying enzyme treated with DNA destroying enzyme did NOT kill the mice—all the other did NOT kill the mice—all the other tests did kill the mice—DNA was the tests did kill the mice—DNA was the factor that caused transformation in factor that caused transformation in bacteria.bacteria.

Hershey-Chase ExperimentHershey-Chase Experiment

BacteriophageBacteriophage

Hershey-Chase ExperimentHershey-Chase Experiment

Was it the protein coat or inner DNA core Was it the protein coat or inner DNA core that was the hereditary material???that was the hereditary material???

Grew “phages” in radioactive P & SGrew “phages” in radioactive P & S Proteins have lots of S but very little P in Proteins have lots of S but very little P in

their chemical makeup.their chemical makeup. DNA has lots of P, but no S.DNA has lots of P, but no S. Look at page 290 in your book.Look at page 290 in your book. Radioactive P found in bacteria prey.Radioactive P found in bacteria prey. Evidence that DNA is hereditary material.Evidence that DNA is hereditary material.

Purines and PyrimidinesPurines and Pyrimidines

Erwin ChargaffErwin Chargaff

Chargaff’s RulesChargaff’s Rules

% of Guanine equals % Cytosine in % of Guanine equals % Cytosine in DNA at all timesDNA at all times

% of Thymine equals % Adenine in % of Thymine equals % Adenine in DNA at all timesDNA at all times

All organisms from bacteria to All organisms from bacteria to bananas to plants to humans obey bananas to plants to humans obey these rules. these rules.

If A is 14% in DNA, what % is C % ?If A is 14% in DNA, what % is C % ?

Rosalind FranklinRosalind Franklin

Watson and CrickWatson and Crick

James WatsonJames Watson Francis CrickFrancis Crick

James Watson is still alive!!!!James Watson is still alive!!!!

““The instant I saw the picture (of the The instant I saw the picture (of the X-ray of DNA by Rosalind Franklin) X-ray of DNA by Rosalind Franklin) my mouth fell open and my pulse my mouth fell open and my pulse began to race!!”began to race!!”

Double HelixDouble Helix

DNADNA

Twisted Ladder or spiral staircase.Twisted Ladder or spiral staircase. Hydrogen bonds hold the purines and Hydrogen bonds hold the purines and

pyrimidines together. A-T C-Gpyrimidines together. A-T C-G 3 hydrogen bonds between G and C3 hydrogen bonds between G and C 2 hydrogen bonds between T and A2 hydrogen bonds between T and A This is termed “base pairing”.This is termed “base pairing”. Chargaff’s rules apply!!!Chargaff’s rules apply!!! Deoxyribose Nucleic AcidDeoxyribose Nucleic Acid