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Foothill High School Science Department DNA & RNA DNA.

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Presentation on theme: "Foothill High School Science Department DNA & RNA DNA."— Presentation transcript:

1 Foothill High School Science Department DNA & RNA DNA

2 Foothill High School Science Department Griffith & Transformation 1928 Studying Natural Bacterial Pneumonia caused by: – Streptococcus pneumoniae Smooth (pathogenic) Rough (non-pathogenic) S. pneumonia in sputum Notice capsule Gram Positive Diplococci

3 Foothill High School Science Department Streptococcus pneumonia Optochin Disc Type 3 VERY Mucoid

4 Foothill High School Science Department Griffith’s Experiments Injected Mice – Smooth – Mice Died – Rough – Mice Didn’t Get Sick – Heat Killed Smooth – Mice Didn’t Get Sick Illness Not Caused By Poison

5 Foothill High School Science Department Transformation Mixed Heat Killed Smooth With Rough Live Bacteria. – Mice Died – Autopsy Revealed Lungs Full Of Smooth Strain of Bacteria HOW?? Rough Bacteria Don’t Kill!

6 Foothill High School Science Department Griffiths Transformation

7 Foothill High School Science Department Transformation 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

8 Foothill High School Science Department Avery & 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

9 Foothill High School Science Department Avery & DNA Treated Extract To DestroyProteinsLipidsCarbohydratesRNA Transformation Still Occurred

10 Foothill High School Science Department Avery & DNA Then They Treated The Extract & Destroyed The DNA Transformation Did NOT Occur DNA Was The Transforming Factor

11 Foothill High School Science Department Avery & DNA Key Concept Avery and other scientists discovered that DNA stores and transmits the genetic information from one generation of an organism to the next generation.

12 Foothill High School Science Department The Structure of DNA Chargaffs Rules – Discovered That Certain Nucleotides Were Always Present In The Same Percentages: – AdenineThymine – Adenine & Thymine – GuanineCytosine – Guanine & Cytosine – % In Each Species Different – Nobody Knew Why

13 Foothill High School Science Department Hershey-Chase Experiment Studied Virus Particles, Especially Bacteriophages Studied Virus Particles, Especially Bacteriophages Martha Chase & Alfred Hershey

14 Foothill High School Science Department Hershey-Chase Experiment Bacteriophages – Composed of DNA or RNA – and a Protein Coat – Figured Whichever Part Entered The Bacteria – Carried The Genes Used Radioactive Markers

15 Foothill High School Science Department Radioactive Markers Grew Viruses In Cultures Containing Grew Viruses In Cultures Containing – Radioactive Phosphorus ( 32 P ) and and – Radioactive Sulfur ( 35 S ) Proteins Contain No Phosphorous DNA Contains No Sulfur

16 Foothill High School Science Department Radioactive Markers Therefore: If The Interior Of The Bacteria Contained : ( 32 P ) Then DNA Contained Genes ( 35 S ) Then Protein Contained Genes Nearly All The Bacteria Contained ( 32 P ) Therefore DNA Contained Genes

17 Foothill High School Science Department Hershey-Chase Bacteriophage (virus that infects bacteria) Outer, Protein Coat Contains Sulfur – No Phosphorus E. coli bacteria (infected by Bacteriophage) Bacteriophage DNA injected into the E. coli Bacteriophage DNA contains Phosphorous but NO Sulfur

18 Foothill High School Science Department Hershey-Chase

19 Foothill High School Science Department Hershey - Chase Key Concept: Hershey and Chase concluded that the genetic material of the bacteriophage was: DNA, not Protein.

20 Foothill High School Science Department The Structure of DNA X-Ray Diffraction – Early 1950’s – Rosalind Franklin Rosalind Franklin Rosalind Franklin – Doesn’t Show Structure But Provides Clues DNA Twisted In Coils Two Strands Nitrogenous Base In Center

21 Foothill High School Science Department Photo 51

22 Foothill High School Science Department Watson & Crick Watson & Crick – Building 3 Dimensional Models – 1953 Saw Franklins X-ray Work – Immediately Recognized What The Structure Had To Be: A Double Helix A Double Helix The Double Helix

23 Foothill High School Science Department The Structure of DNA Scientists still didn’t know: Scientists still didn’t know: – How information was carried between generations – How genes were structured – How genes were copied

24 Foothill High School Science Department The Structure of DNA DNA is a long Molecule of repeating nucleotides DNA is a long Molecule of repeating nucleotides Each nucleotide has 3 parts: Each nucleotide has 3 parts: – 5 Carbon Sugar (Deoxyribose) – 1 Phosphate Group – 1 Nitrogenous Base

25 Foothill High School Science Department The Structure of DNA 4 Nitrogenous Bases There are 4 Nitrogenous Bases in DNA The 4 Bases are two types: – Purines – Purines which are Double Ring Molecules Adenine Guanine – Pyrimidines – Pyrimidines which are Single Ring Molecules Cytosine Thymine

26 Foothill High School Science Department Purines Pyrimidines

27 Foothill High School Science Department Watson & Crick Key Concept: Watson & Crick’s Model of DNA was a Double Helix, in which Two (2) Strands were wound around each other.

28 Foothill High School Science Department The Structure of DNA Nitrogenous Bases Forms Rungs of DNA Ladder Phosphate/Deoxyribose Form Sides of the DNA Ladder

29 Foothill High School Science Department Watson & Crick Discovered The Double Helix Held Together By Hydrogen Bonds Between The Nitrogenous Bases Base Pairing A:TG:C A:T and G:C Explained Chargaff’s Rule

30 Foothill High School Science Department Double Helix


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