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DNA

Central Dogma of Biology. DNA. Mostly only in viruses. In all cells. RNA. Protein. Processes in the central dogma. Cellular processes. (Mostly) RNA virus processes. DNA. Replication. Reverse transcription. Transcription. RNA. RNA replication. Translation. Protein.

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DNA

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  1. Central Dogma of Biology DNA Mostly only in viruses In all cells RNA Protein

  2. Processes in the central dogma Cellular processes (Mostly) RNA virus processes DNA Replication Reverse transcription Transcription RNA RNA replication Translation Protein

  3. Enzymes in the central dogma Cellular enzymes (Mostly) RNA virus enzymes DNA DNA polymerase Reverse transcriptase RNA polymerase RNA-dependent RNA polymerase RNA Ribosome Protein

  4. Genetic material is transferable between bacteria Streptococcus pneumoniae Griffith, 1928 Fig. 2.2

  5. The genetic material is DNA Heat killed S strain treated with: - Phenol => still infectious - Proteinase (trypsin, chymotrypsin) => still infectious - UV light => no longer infectious - RNase => still infectious - DNase => no longer infectious Avery, MacLeod, McCarthy, 1944 => Genetic material is DNA! Based on Fig. 2.2

  6. The genetic material of bacteriophage T2 is DNA Hershey, Chase, 1952 Fig. 2.4 Some viruses use RNA as genetic material (e.g. HIV, herpesviruses etc)!

  7. Scrapie is an infectious brain disease in sheep (related to Kuru and CJD in humans and mad cow disease in cows). Researchers isolated brain extracts from sick sheep and injected them into brains of hamsters, and observed the following: - Untreated brain extract => infectious - UV light treated => still infectious - RNase treated => still infectious - DNase treated => still infectious - Phenol treated => no longer infectious - Proteinase (trypsin, chymotrypsin) treated => no longer infectious What is the transforming material? - Clicker Question - A: DNA B: RNA C: Protein D: There is no transforming material

  8. A nucleotide is composed of a sugar, a phosphate and a base

  9. Nitrogenous bases: Nitrogenous bases: Phosphoric acid Phosphoric acid The chemical nature of DNA and RNA DNA RNA Adenine (A) Cytosine (C) Guanine (G) Thymine (T) Adenine (A) Cytosine (C) Guanine (G) Uracil (U) Sugar: 2’ deoxyribose Sugar: ribose

  10. The sugars (RNA) (DNA) Fig. 2.6

  11. The bases (RNA + DNA) (RNA + DNA) (RNA only) (RNA + DNA) (DNA only) Fig. 2.5

  12. Nucleosides (=sugar+base, no phosphate) Fig. 2.9

  13. Nucleotides (= nucleoside phosphates)

  14. - Clicker Question - Which of these nucleotides is used in transcription? (A) (B) (C) (D) (E)

  15. 5’ end 3’ end Nucleotide polymer 5’ TCA 3’

  16. Base pairs

  17. The double-helix

  18. A B Z Different polynucleotide double-helix structures Inclination of base pair from horizontal Residues per turn Form Pitch (Å) Most dsRNA A 24.6 ~11 +19º B 33.2 ~10 -1.2º Z 45.6 12 -9º Most DNA Rare

  19. - Clicker Question - Many DNA binding transcription factors recognize specific DNA sequences. Which contacts are likely most important for the sequencespecificity of transcription factors? A: Contacts between the transcription factor and the DNA phosphates. B: Contacts between the transcription factor and the DNA deoxyriboses. C: Contacts between the transcription factor and the DNA bases. D: All of the above. Which contacts are important for binding affinity?

  20. Although G=C and A=T are true for every organism, the ratio of G+C versus A+T vary from organism to organism

  21. The DNA content varies between organisms * * * * *

  22. Two DNA strands can be separated by heating, a process called DNA denaturation or DNA melting The temperature at which the DNA strands are half denatured is called the melting temperature, or Tm. Tm of a DNA is largely determined by its G/C% (The more G/C the higher Tm) and the length (the longer the higher Tm) (Think of it as the more total hydrogen bonds, the higher temp to denature). Other ways of denaturing DNA?

  23. anneal Annealing: The process of reuniting separated DNA strands (also called renaturation). Hybridization: The process of annealing a DNA strand with a complementary RNA strand or DNA strand from a different origin.

  24. - Clicker Question - Which of the following DNAs has the lowest Tm? A: 5’-GCATGCATGC-3’ 3’-CGTACGTACG-5’ B: 5’-GATTGATTGA-3’ 3’-CTAACTAACT-5’ C: 5’-GATTGATTGATTA-3’ 3’-CTAACTAACTAAT-5’ D: 5’-GCATGCATGCGCC-3’ 3’-CGTACGTACGCGG-5’ E: 5’-GGCGCGCCGC-3’ 3’-CCGCGCGGCG-5’

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