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Cell Reproduction Unit Pictures The Code of Life
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Cell Reproduction Unit Pictures
Topic 1 Experimental Evidence, Activity 1: What is the code of Life
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Cell Reproduction Unit Pictures
OBJ 1 Freddy G (Griffith) Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Control (no growth) Dies of pneumonia Lives Live, disease-causing bacteria (smooth colonies)
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Cell Reproduction Unit Pictures
OBJ 1 Ozzy A (Avery)
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Obj 1 Ozzy A (Avery)
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Figure 16.2b The Hershey-Chase experiment
OBJ 2 Cell Reproduction Unit Pictures
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Activity A: Experimental Evidence Summary
Question? Observation Inference Frederick Griffith (R, S bacteria effects on mice) What causes virulence in bacteria? R strain bacteria transform into living S bacteria in the presence of dead S bacteria Virulence was transferred from S to R bacteria Oswald Avery (Griffith’s exp. with enzymes) What is being transferred from S to R bacteria? Dead S bacteria do not transfer virulence when DNA is digested with an enzyme DNA is the molecule for information transfer (molecule of inheritance), not protein Hershey and Chase (bacteriophages) What type of molecule is injected into bacteria (DNA or protein) Radioactive DNA found inside of bacteria, radioactive protein found outside of bacteria
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Cell Reproduction Unit Pictures DNA Structure and Replication
Topic 2 DNA Structure and Replication
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Nucleic Acids DNA and RNA Monomer - nucleotide
Unit 1: Biochemistry and Digestion OBJ 3 Nucleic Acids DNA and RNA Monomer - nucleotide Five-carbon sugar (deoxyribose or ribose) Phosphate group Nitrogenous base Adenine Guanine Cytosine Thymine (DNA only) Uracil (RNA only)
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Cell Reproduction Unit Pictures
OBJ 3 DNA and RNA Nucleotides Polymer – DNA or RNA Monomers – Nucleotides DNA – Cytosine, Thymine, Adenine, Guanine RNA - Cytosine, Adenine, Uracil, Guanine Single rings Double rings
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DNA Structure - Putting it all together…
Obj 4,5,6 DNA Structure - Putting it all together… Hershey-Chase and Avery– Convinced the world that DNA was the molecule of inheritance Chargaff’s Rule – data collected showed that there are equal numbers of Adenine(A) to Thymine(T) and Cytosine(C) to Guanine (G) Implied that the nucleotides are related in some way
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Relative Proportions (%)of Bases in DNA
Cell Reproduction Unit Pictures OBJ 5 Relative Proportions (%)of Bases in DNA Organism A T G C Human Chicken Grasshopper Sea Urchin Wheat Yeast E. coli Chargaff saw that within a species, the amount of thymine always equaled the amount of adenine and cytosine equaled guanine
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DNA Structure - Putting it all together…
Obj 4,5,6 DNA Structure - Putting it all together… Hershey-Chase and Avery– Convinced the world that DNA was the molecule of inheritance Most of the Chemical minds are now working on determining the structure of DNA Chargaff’s Rule – data collected showed that there are equal numbers of Adenine(A) to Thymine(T) and Cytosine(C) to Guanine (G) Implied that the nucleotides are related in some way Rosalind Franklin – X-ray crystallographer Produced ‘Photo 51’ image of DNA, showing consistent 2 nm diameter of DNA and parallel strands
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Figure 16.4 Rosalind Franklin and her X-ray diffraction photo of DNA
Cell Reproduction Unit Pictures OBJ 4 X-Ray Crystallography showed the double helix shape and showed that the helix was uniform in shape
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Cell Reproduction Unit Pictures
OBJ 4, 6 The only way it could be uniform in shape if is a purine always bonds with a pyrimidine
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DNA Structure - Putting it all together…
Obj 4,5,6 DNA Structure - Putting it all together… Hershey-Chase and Avery – Convinced the world that DNA was the molecule of inheritance Most of the Chemical minds are now working on determining the structure of DNA Chargaff’s Rule – data collected showed that there are equal numbers of Adenine(A) to Thymine(T) and Cytosine(C) to Guanine (G) Implied that the nucleotides are related in some way Rosalind Franklin – X-ray crystallographer Produced ‘Photo 51’ image of DNA, showing consistent 2 nm diameter of DNA and parallel strands James Watson, Francis Crick (and Maurice Wilkins) Put it all together, make the first model of DNA Win the Nobel Prize
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Watson and Crick Model of DNA
Known: Nucleotide structure and types (previous scientists) Nucleotide abundance (Chargaff) Double stranded, twisting (Franklin) Nitrogenous bases pointing inwards (Franklin) Inference (W and C) Double Helix model Base pairing Sugar-phosphate backbone
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Cell Reproduction Unit Pictures
OBJ 7 Base Pairing Adenine and Thymine make 2 hydrogen bonds Guanine and Cytosine make 3 hydrogen bonds Watson and Crick literally made puzzle pieces to see how they fit together and discovered that adenine could make 2 hydrogen bonds with thymine and guanine could make 3 with cytosine “Complementary bases”
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Cell Reproduction Unit Pictures
OBJ 7 Sugar-phosphate Backbone Covalent bonds between phosphate groups and sugars (Deoxyribose) Forms via dehydration synthesis (polymerization) Sugar-phosphate backbone Nitrogenous bases stick into middle The strands are antiparallel - they run in opposite directions the side that ends in sugar is 3’ and the side that ends in phosphate is 5’
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The Double Helix - structure
Cell Reproduction Unit Pictures OBJ 7 The Double Helix - structure Base pair = C-G and A-T We say C and G are complementary and A and T are complementary We say that human DNA contains over 6 billion base pairs - how many nucleotides?
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Cell Reproduction Unit Pictures
OBJ 7 DNA strands are antiparallel Important because.. Enzymes that interact with DNA only work in the 3’ to 5’ direction Shape controls function!
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Cell Reproduction Unit Pictures
OBJ 8 DNA Replication Semiconservative model Each strand of DNA is used as a template Free nucleotides are connected according to base pairing rules A to T C to G Results in two identical strands of DNA Several enzymes make this work The two parent strands become templates for assembly of a complementary strand from a supply of free nucleotides The new strands are called daughter strands
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Cell Reproduction Unit Pictures
OBJ 8 The process is called semi-conservative because half of the parental molecule is maintained in each daughter molecule
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Closer Look at DNA Replication
OBJ 8 Closer Look at DNA Replication Replication involves many enzymes!!! DNA Helicase – unwinds the helix and “unzips” the base pairs Forms the replication fork
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Closer Look at DNA Replication
OBJ 8 DNA Polymerase – adds nucleotides to the template strand, creating a daughter strand Several slightly different DNA polymerases work together to do this DNA Polymerase only works in the 3’ to 5’direction Creates a full Leading strand Creates a segmented Lagging strand
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Closer Look at DNA Replication
OBJ 8 DNA Ligase – Enzyme that closes the gaps in the lagging strand of DNA
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THE END
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Figure 16.8 Three alternative models of DNA replication
Cell Reproduction Unit Pictures
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Cell Reproduction Unit Pictures
Figure The Meselson-Stahl experiment tested three models of DNA replication (Layer 4) Cell Reproduction Unit Pictures
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