NL 8:30-2:30 Weather Plan? Room #8:30 – 9:45 AP BIOLOGY I Jolene Jacquet 226 Lab Review 1-6 AP...
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- NL 8:30-2:30 Weather Plan? Room #8:30 9:45 AP BIOLOGY I Jolene
Jacquet 226 Lab Review 1-6 AP BIOLOGY II Nancy Bishop 228 DNA &
Protein Synthesis AP BIOLOGY III Cindy Brainard / Brian Elliott 229
Evolution Major Concepts &Hardy Weinberg (Brainard)
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- How do we know DNA is the genetic material
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- What is the genetic material? Fredrick Griffith How do certain
bacteria cause pneumonia? 2 strains (types) of Streptococcus
pneumonia Smooth when grown in petri dish smooth edged colonies and
shiny Rough when grown in petri dish rough edged colonies and not
shiny SMOOTH COLONIES ARE PATHOGENIC disease causing ROUGH COLONIES
ARE USUALLY DESTROYED BY HOST IMMUNE SYSTME
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- bacterium smooth strain capsule rough strain no capsule
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- ??????????
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- Does the capsule cause disease? DEAD S cells were mixed with
live R cells. Bacteria isolated from blood of dead mice were S
strain and produced more S strain cells Change was permanent and
heritable capsule did not cause disease.
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- TRANSFORMATION Something in dead, disease-causing bacteria
turned harmless bacteria into killers! He called this process
TRANSFORMATION Some factor in dead pathogens turned harmless
bacteria into pathogens!
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- What is the transforming factor? C (somatic) carbohydrate,
nucleoproteins, free nucleic acids of both the yeast [RNA] and
thymus [DNA] types, lipids and other cell constituents. Try to find
in that complex mixture the active principle..!! Try to isolate and
chemically identify the particular [transforming]
substance....!Some job--full of heartaches and heartbreaks. But at
last perhaps we have it.... Oswald Avery
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- What is the transforming factor? Oswald Avery and colleagues
Made extract of bacteria Destroyed proteins, lipids, carbohydrates,
and nucleic acids (RNA and DNA) one-by- one with enzymes When DNA
was destroyed by enzymes the cells did not become pathogenic
Conclusion??????
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- Many people remained unconvinced that DNA was the genetic
material! Many thought protein must be the genetic material.
Protein is more complicated 20 amino acids DNA is made of only 4
bases adenine, guanine, cytosine and thymine Protein had greater
heterogeneity and specificity of function Little was know about
nucleic acids at the time
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- EVIDENCE DNA IS GENETIC MATERIAL Alfred Hershey and Martha
Chase Worked with a simple system: E. coli bacteria and
bacteriophages viruses that infect bacteria
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- EVIDENCE DNA IS GENETIC MATERIAL VIRUSES are not cells. Consist
of nucleic acid wrapped in a protein coat. Must infect a cell in
order to reproduce. bacteria
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- EVIDENCE DNA IS GENETIC MATERIAL How could they determine
whether DNA or protein from phage entered cell? Protein has sulfur,
DNA does not grow phages in radioactive sulfur 35 S DNA has
phosphorus, protein does not grow phages in radioactive phosphorus
32 P Virus capsid protein coat labeled with 35 S Virus core DNA
labeled with 32 P Infect the bacteria and see which one enters the
cell
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- EVIDENCE DNA IS GENETIC MATERIAL Radioactive DNA entered the
cell but radioactive protein stayed outside. Conclusion?
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- What does DNA look like? Watson and Crick Rosalind
Franklin
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- HOW IS DNA REPLICATED? Meselson and Stahl Use radioactive
isotopes to track old and new strands of DNA Use centrifugation to
separate DNA molecules by mass and CHASE
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- HOW DO WE KNOW WHICH MODEL IS CORRECT?
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- First make the original DNA HEAVY
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- http://www.sumanasinc.com/webcontent/anima
tions/content/meselson.html
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