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DNA and RNA Replication, Transcription, and Translation

DNA and RNA Replication, Transcription, and Translation. Genetic Controversy Two schools of thought a. Some said protein was material b. Some said DNA was material How was the controversy settled? - The scientific experiments of Griffith, Avery, Hershey and Chase.

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DNA and RNA Replication, Transcription, and Translation

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  1. DNA and RNA Replication, Transcription, and Translation

  2. Genetic Controversy Two schools of thought a. Some said protein was material b. Some said DNA was material How was the controversy settled? - The scientific experiments of Griffith, Avery, Hershey and Chase

  3. Griffith and Transformation - 1928 - England - Trying to develop a vaccine against pneumonia causing bacteria - Two strains - S(smooth) and R(rough)

  4. Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control(no growth) Harmless bacteria (rough colonies) Disease-causing bacteria (smooth colonies) Heat-killed, disease-causing bacteria (smooth colonies) Dies of pneumonia Lives Dies of pneumonia Lives Live, disease-causingbacteria (smooth colonies)

  5. RESULTS - Showed that heat killed S strain and live R strain would kill mice - Something was “transforming” the R strain to an S strain - Called it transformation - What was the material?

  6. Oswald Avery - 1944 - Wanted to identify Griffith’s transforming material - Used two enzymes a. protein killing b. DNA killing - Showed that no transforming took place when DNA “killed”

  7. D. Hershey and Chase - 1952 - Working with a bacteriophage - Virus that infects bacteria - Made of only two things a. protein coat b. DNA (genetic) core

  8. Hershey and Chase Phage infectsbacterium Bacteriophage with phosphorus-32 in DNA Radioactivity inside bacterium Phage infectsbacterium No radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat

  9. Recap:Was DNA or protein injected? - DNA has phosphorus - Protein has sulfur - Used radioactive phosphorus 32P and radioactive sulfur 35S - Let virus infect bacteria - New viruses full of 32P DNA was being injected!

  10. The Components and Structure of DNA 1. Called deoxyribonucleic acid 2. Long and thread-like (twisted) 3. Many subunits linked together 4. Subunits called nucleotides 5. 1000’s in a chain-like structure

  11. The structure of a nucleotide 1. Phosphate group - same in all 2. Five carbon sugar a. deoxyribose sugar 3. Nitrogenous base - 4 different ones that name the nucleotide

  12. Nitrogenous Bases 1. Are different in each nucleotide 2. Names of the four bases a. adenine (A) b. guanine (G) c. thymine (T) d. cytosine (C) Two classes of bases A. purines 1) large double ring 2) A & G B. pyrimidines 1) small single ring 2) T & C

  13. Purine and Pyrimidine Structure

  14. H. Chargaff - 1949 - Studying the amounts of bases in DNA of living things - His results showed that: a. A always = T b. C always = G - Called Chargaff’s rule - Also called the base pair rule

  15. The molecule is completed… - Franklin and her X-ray diffraction picture showed a helix Watson and Crick adds that it is a double helix with bases in the middle - Called it a “spiral staircase” - Strands are complements of each other - Think of a step ladder a. “sides” are alternating sugar and phosphate groups b. “rungs” are base pairs 1) A = T 2) C = G

  16. Nucleotide Hydrogen bonds Sugar-phosphate backbone Adenine Thymine Cytosine Guanine

  17. Chromosomes and DNA Replication A. DNA Can Make Copies of Itself 1. Process called replication 2. Done during S phase 3. Needed for new cells 4. DNA unwound using helicases 5. Hydrogen bonds broken between bases 6. DNA polymerase puts new nucleotides in place (A to T and C with G) 7. New copy just like original

  18. DNA Double-stranded Deoxyribose Thymine RNA Single-stranded Ribose Uracil From Genes To Proteins

  19. RNA (ribonucleic acid) 3 forms of RNA mRNA (messenger) tRNA (transfer) rRNA (ribosomal) RNA is used to take the information in DNA and make proteins (gene expression) 2 stages of gene expression Transcription Translation

  20. The Big Idea… During gene expression, the info in DNA is first transcribed as mRNA and then translated via tRNA and used to build a protein.

  21. From Genes To Proteins… 1. Transcription: making mRNA from DNA to carry information to the ribosomes.

  22. - ALL organisms have a genetic code made of three nucleotide sequences called codons. - Codons correspond to particular AA and stop signals.

  23. The Genetic Code

  24. The Genetic Code

  25. From Genes To Proteins… 2. Translation: Using tRNA to build proteins from the information in mRNA. - Each tRNA molecule carries an amino acid to the ribosomes, by matching its anticodon to a specific codon from the mRNA http://www.youtube.com/watch?v=NJxobgkPEAo

  26. GENETIC MUTATIONS Mutations (gene or chromosomal) • Changes in DNA • Effect depends on where mutation occurs (body or sex cell) & what type of mutation • Can be helpful, harmful, or neutral

  27. Different Types of Gene Mutations • Substitutions = UGU to UGC • Effect depends on translation • Insertions = nucleotides added • Deletions = nucleotides deleted • Transposons= DNA segments move spontaneously from one location to another in the same DNA molecule

  28. Ex. THE CAT ATE THE RAT (meaningful) • Deletion of C = THE ATA TET HER AT (meaningless)

  29. Types of Chromosomal Mutations • Deletions (whole or part deleted) • Duplications (extra copies of parts) • Inversions (reverses parts of chromosomes) • Translocations (parts break off and relocate) 31

  30. Causes of Mutations? • Spontaneous • Mutagens (come from environment) • UV light • Chemicals • Carcinogens (cancer causing)

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