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Biology 30

Biology 30. Nucleic Acids. DNA RNA. Students will explain classical genetics at the molecular level. Summarize the historical discovery of the DNA molecular structure by Franklin, Watson and Crick Describe how genetic information is contained in the sequence of bases in DNA

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Biology 30

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  1. Biology 30 Nucleic Acids DNA RNA

  2. Students will explain classical genetics at the molecular level • Summarize the historical discovery of the DNA molecular structure by Franklin, Watson and Crick • Describe how genetic information is contained in the sequence of bases in DNA • Describe DNA replication

  3. Some History • 1928 • Frederick Griffith (British) • Studied Streptococcus Pneumoniae • pneumonia bacteria • two genetic strains • Colonies appeared smooth (S type) • Surrounded by a mucous coat or capsule • Colonies that appeared rough (R type)

  4. R Bacteria

  5. R Bacteria S Bacteria

  6. R Bacteria S Bacteria Dead R Bacteria

  7. R Bacteria S Bacteria Dead R Bacteria

  8. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria

  9. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria

  10. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria Dead S & Live R

  11. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria Dead S & Live R

  12. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live R

  13. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live R

  14. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live R DNA of S and live R

  15. R Bacteria S Bacteria Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live R DNA of S and live R

  16. In 1928, Frederick Griffith performed an experiment using pneumonia bacteria and mice. This was one of the first experiments that hinted that DNA was the genetic code material. • He used two strains of Streptococcus pneumoniae: • a “smooth” strain which has a polysaccharide coating around it that makes it look smooth when viewed with a microscope, • a “rough” strain which doesn’t have the coating, thus looks rough under the microscope. • When he injected live S strain into mice, the mice contracted pneumonia and died. • When he injected live R strain, a strain which typically does not cause illness, into mice, as predicted they did not get sick, but lived.

  17. Thinking that perhaps the polysaccharide coating on the bacteria somehow caused the illness and knowing that polysaccharides are not affected by heat, Griffith then used heat to kill some of the S strain bacteria and injected those dead bacteria into mice. • This failed to infect/kill the mice, indicating that the polysaccharide coating was not what caused the disease, but rather, something within the living cell. • Since Griffith had used heat to kill the bacteria and heat denatures protein, he next hypothesized that perhaps some protein within the living cells, that was denatured by the heat, caused the disease.

  18. He then injected another group of mice with a mixture of heat-killed S and live R, and the mice died! • When he did a necropsy on the dead mice, he isolated live S strain bacteria from the corpses. • Griffith concluded that the live R strain bacteria must have absorbed genetic material from the dead S strain bacteria, and since heat denatures protein, the protein in the bacterial chromosomes was not the genetic material. • This evidence pointed to DNA as being the genetic material.

  19. Functions of DNA • Controls cellular activities of an organism by • Coding for structural proteins • Coding for enzymes

  20. Nucleic Acids • DNA • Deoxyribonucleic Acid • Genetic material • Can self-replicate • Made up of Nucleotides • Shape = double helix • A twisted rope ladder • A full twist every 10 nucleotides

  21. DNA Discovery • Rosalind Franklin was using X-Ray Diffraction to study DNA • Her work allowed Watson and Crick to come up with model of DNA • Findings presented in 1953 • Visually confirmed in 1969

  22. Chromosome Section of Chromosome Section of DNA Double Helix

  23. Nucleotides • Nucleotides are composed of • A sugar • five carbons • Deoxyribose • A phosphate • PO4- • One of 4 nitrogen bases • Adenine [A] • Thymine [T] • Cytosine [C] • Guanine [G] The sugar-phosphate groups are the side rails of ladder and the the nitrogen bases are the rungs

  24. Nucleotides • The two strands of DNA are complimentary because the nitrogen bases bond with each other according to some rules. • Adenine will only bond with Thymine • Guanine will only bond with Cytosine • Nitrogen bases bond via hydrogen bonds. • These break over 70oC (denature)

  25. DNA REPLICATION • DNA must have the ability to create an exactduplicate of itself • The sequence in one strand determines precisely what the sequence of nucleotides in the other strand will be. (A-T, G-C)

  26. DNA REPLICATION • The hydrogen bonds holding the two complimentary strands together break • DNA strands separate • Free floating complimentary nucleotides match up with nucleotides on the parent DNA strand. • Catalyzed by DNA polymerase • New, semi-conservative strands are formed

  27. DNA REPLICATION • Semi-conservative • The daughter strands are made up of one half old strand on one half new strand • The DNA unzips due to the hydrogen bonds between the bases being broken (DNA Helicase) • These exposed bases attract free floating bases, which are attached to the chain by DNA polymerase.

  28. X

  29. Students will explain classical genetics at the molecular level • Describe RNA transcription • Describe how genetic information is translated into amino acid chains in proteins • Explain how mutations result in abnormalities or create genetic variability • Explain how base sequences in nucleic acids give evidence for evolution

  30. DNA RNA DNA vs RNA

  31. DNA Double stranded RNA DNA vs RNA

  32. DNA Double stranded RNA Single stranded DNA vs RNA

  33. DNA Double stranded Deoxyribose sugar RNA Single stranded DNA vs RNA

  34. DNA Double stranded Deoxyribose sugar RNA Single stranded Ribose sugar DNA vs RNA

  35. DNA Double stranded Deoxyribose sugar Nitrogen bases Cytosine RNA Single stranded Ribose sugar DNA vs RNA

  36. DNA Double stranded Deoxyribose sugar Nitrogen bases Cytosine Guanine RNA Single stranded Ribose sugar DNA vs RNA

  37. DNA Double stranded Deoxyribose sugar Nitrogen bases Cytosine Guanine Adenine RNA Single stranded Ribose sugar DNA vs RNA

  38. DNA Double stranded Deoxyribose sugar Nitrogen bases Cytosine Guanine Adenine Thymine RNA Single stranded Ribose sugar DNA vs RNA

  39. DNA Double stranded Deoxyribose sugar Nitrogen bases Cytosine Guanine Adenine Thymine RNA Single stranded Ribose sugar Nitrogen bases Cytosine DNA vs RNA

  40. DNA Double stranded Deoxyribose sugar Nitrogen bases Cytosine Guanine Adenine Thymine RNA Single stranded Ribose sugar Nitrogen bases Cytosine Guanine DNA vs RNA

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