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Understanding DNA: Key Scientists and Concepts in Genetics

This chapter delves into the essential contributions of prominent scientists like Griffith, Avery, Hershey-Chase, Chargaff, Franklin, and Watson-Crick towards our understanding of DNA and its processes. Key experiments involving strains of bacteria and mice illustrate the definition of terms such as "virulent." The text explains the transformation process, defines crucial enzymes, and explores the structure of DNA, including the double helix model and base pairing rules. It also covers chromosome structure and DNA replication, highlighting critical stages and the role of enzymes in maintaining genetic integrity.

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Understanding DNA: Key Scientists and Concepts in Genetics

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  1. DNA and its Processes • Chapter 12 • Material on Midterm

  2. Section 12-1: DNA • There are several scientists that have contributed to our understanding of DNA • Griffith • Avery • Hershey-Chase • Chargaff • Franklin • Watson-Crick

  3. Griffith

  4. Section 12-1: DNA • Answer these questions • What are the two types of strains? • Seeing what happens to mice injected with virulent strains, what do you think “virulent” means?

  5. Section 12-1: DNA • Frederick Griffith • Responsible for _____________________ • Process in which one strain of bacteria is changed by gene(s) from another strain • Worked with mice and pneumonia • Mice that were injected with rough or heat-killed smooth strain __________ • Mice that had the smooth strain _______ • Mice that had the heat-killed smooth but living rough _____. • Why?

  6. Avery

  7. Section 12-1: DNA • Answer these questions • What does the “S” strain do to mice again? • What enzyme destroys proteins? • What enzyme destroys RNA? • What enzyme destroys DNA? • Which enzyme prevented the smooth strain to grow?

  8. Section 12-1: DNA • Oswald Avery • Responsible for determining that the molecule important in transformation was _______________________ • Took heat-killed bacteria and made extract • Enzymes for lipids, proteins, and carbohydrates—________ • Still transformation of smooth strain • Enzymes for nucleic acid—_____________ • Smooth strain not transformed

  9. Hershey & Chase

  10. Section 12-1: DNA • Answer these questions • Why did they use radioactive sulfur for identifying protein? (Think about the elements in protein!) • Why did they use radioactive phosphorus for identifying DNA? (Think about the elements in DNA!) • Which is more dense—DNA or protein? • What remained in the bacteria—DNA or protein?

  11. Section 12-1: DNA • Alfred Hershey and Martha Chase • Determined that the ___________________ is made out of DNA, not protein • Used radioactive labels • _________-35 for protein—CHOSN for protein • ______________-32 for nucleic acid—CHOPN • Genetic material glowed with P-32…_____

  12. Section 12-1: DNA • Chargaff • Looked at numerous organisms • Compared concentrations of nitrogenous bases (bases) • What do you notice? ___________________________ Chargaff had no idea WHY this was happening!

  13. Section 12-1: DNA • Rosalind Franklin • Used X-ray diffraction to study image of DNA • __________ shape • Twisted strands • ___ strands • Bases near ________

  14. Section 12-1: DNA • What words do you not recognize in the paper? Make a list. • How does the length of the paper compare to a normal scientific article (around 5 pages)? • Why don’t they like Pauling’s and Corey’s model (2 reasons)? • How many helical chains do they propose? • How many base pairs (residues) are in the chain before it repeats? • Where are the phosphates located? • What type of bond joins the bases? • What base pairing rules do they suggest? • What is the sugar?

  15. Section 12-1: DNA • Built 3-D models of DNA • Used work of everyone before them • Model: double helix • Twisted ladder • H-bonds between nitrogenous bases • Base pairing: A with T, G with C • EXPLAINS CHARGAFF

  16. SUM IT UP!

  17. 12-1: DNA • Components & Structure of DNA • What are the monomers and polymers of nucleic acid? ____________ ___________ • __________-stranded • Each nucleotide is made up of three parts • ___________________ • _____________________ • 4 types • ______________________ • Deoxyribose

  18. 12-1: DNA • 4 different nitrogenous bases • Guanine (__) • Adenine (__) • Cytosine (__) • Thymine (__) __ pairs up with __, and __ pairs up with __

  19. 12-1: DNA The Sugar and the Phosphate group are the ____________ of DNA (covalent bonds) • Role of hydrogen bonds • SUMMARY:

  20. Section 12-1: DNA • Purines • ___ rings • Nucleotide __denine • Nucleotide __uanine • Pyridimes • ___ ring • Nucleotide __hymine • Nucleotide __ytosine Two styles of nucleotides based on size Ones with “y” are pyrimidines Longer word; less rings

  21. SUMITUP

  22. 12-2: Chromosomes and DNA Replication • Think back to mitosis…What happens in the “S” phase of interphase?

  23. 12-2: Chromosomes and DNA Replication • When DNA goes through mitosis, it __________ for easy sorting and separation • When its thin, it’s chromatin • Wrapped around histone proteins like beads on a string • Coils up • Coils coil up • A chromosome is the _____________ form of DNA

  24. 12-2: Chromosomes and DNA Replication • The path to condensation

  25. 12-2: Chromosomes and DNA Replication • Your turn!

  26. DNA condensation • DNA replication • Goal: two ___________ strands of DNA • General steps: • ________ double-strands • _____ new base pairs • ______________

  27. 12-2: Chromosomes and DNA Replication If I were an enzyme… • DNA Replication • DNA helicase comes in and __________ the double helix • _______ primers are added • DNA ________________ ‘lands’ on primers and adds new base pairs • Two identical daughter strands result

  28. 12-2: Chromosomes and DNA Replication • Parent strand • DNA helicase separates • DNA Polymerase adds • DNA ligase cleans up

  29. 12-2: Chromosomes and DNA Replication • It the parent strand is AATCCG, what will the result be? TTAGGC • If we are looking at ONE HALF of a DNA strand for DNA polymerase to add bases to, what would the other half be? GTCAGTTCCATCCTAG

  30. 12-2: Chromosomes and DNA Replication • SUM IT UP!

  31. 12-3: RNA and Protein Synthesis • Components & Structure of RNA • What are the monomers and polymers of nucleic acid? ____________ ___________ • _________-stranded • Each nucleotide is made up of three parts • _____________ • __________________ • 4 types • 5-carbon sugar • ___________

  32. 12-3: RNA and Protein Synthesis • 4 different nitrogenous bases • Guanine (G) • Adenine (A) • Cytosine (C) • Uracil (___) A pairs up with U, and G pairs up with C

  33. 12-3: RNA and Protein Synthesis

  34. 12-3: RNA and Protein Synthesis

  35. 12-3: RNA and Protein Synthesis • Sum it up!

  36. 12-3: RNA and Protein Synthesis • Messenger RNA • ___RNA • ____________ copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell Involved in protein synthesis

  37. 12-3: RNA and Protein Synthesis • Ribosomal RNA • ____RNA • RNA that makes up a major part of the ___________ • Site of protein synthesis ALSO involved in protein synthesis

  38. 12-3: RNA and Protein Synthesis • Transfer RNA • ___RNA • _____________ amino acid to ribosome during protein synthesis And STILL involved in protein synthesis

  39. SUM IT UP

  40. 12-3: RNA and Protein Synthesis • Transcription • Goal: make a strand of __________ that “pairs up” with a template strand of DNA • _________________ strand • Steps • _______ double helix • _____ in RNA bases • Break away and ______________

  41. 12-3: RNA and Protein Synthesis • Transcription • ____________________ does the job of DNA helicase and DNA polymerase combined • _________ and adds ________, but only to the TEMPLATE strand (coding strand)

  42. 12-3: RNA and Protein Synthesis • It the parent strand is AATCCG, what will the result be if the TOP TTAGGCstrand istranscribed? • If we are looking at ONE HALF of a DNA strand for RNA polymerase to add bases to, what would the other half be? GTCAGTTCCATCCTAG

  43. 12-3: RNA and Protein Synthesis • SUM IT UP • Write TWO LINES about the similarities between replication and transcription • Write TWO LINES about the differences between replication and transcription

  44. 12-3: RNA and Protein Synthesis • Genetic Code • What do you see?

  45. 12-3: RNA and Protein Synthesis • The “code” in mRNA specifies the type and order of amino acids • REWIND: amino acids are the monomers of _________ • The goal of the code is to help ________________!

  46. 12-3: RNA and Protein Synthesis • Try the code! • AUG • AUU • UAC • CAC • GGG • UAC • UUU • UAG • Most important 4 • UAA, UAG, UGA • _________ • AUG • “________” • Also MET

  47. 12-3: RNA and Protein Synthesis • Translation • Goal: Make a polypeptide chain (_________) from the information stored in mRNA • Involves all three types of RNA! • Steps • Have mRNA go in ribosome • Ribosome reads codons • tRNA brings in correct amino acids • Protein is built

  48. 12-3: RNA and Protein Synthesis • Translation • ___________ is site of protein synthesis • mRNA strand is _______________ • Ribosome “starts” at the start codon • _______

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