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DNA Structure, Replication, and Organization (DNA 구조 , 복제 그리고 체계 )

DNA Structure, Replication, and Organization (DNA 구조 , 복제 그리고 체계 ). Chapter 14. DNA 의 디지털 모형 (X- 선 구조 데이터에 근거 ). Why It Matters. Deoxyribonucleic acid (DNA) molecule forms the genetic material of all living organisms. 그림 14.1. 1953 년 DNA 구조의 모형을 보여주고 있는 왓슨과 크릭 .

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DNA Structure, Replication, and Organization (DNA 구조 , 복제 그리고 체계 )

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  1. DNA Structure, Replication, and Organization (DNA 구조, 복제 그리고 체계) Chapter 14

  2. DNA의 디지털 모형 (X-선 구조 데이터에 근거)

  3. Why It Matters • Deoxyribonucleic acid (DNA) molecule forms the genetic material of all living organisms 그림 14.1. 1953년 DNA 구조의 모형을 보여주고 있는 왓슨과 크릭.

  4. 14.1 Establishing DNA as the Hereditary Molecule • Griffith found a substance that could genetically transform pneumonia bacteria (폐렴균 박테리아) • Avery and coworkers identified DNA as the molecule that transforms rough Streptococcus to the infective form • Hershey and Chase found the final evidence establishing DNA as the hereditary molecule

  5. Griffith’s Experiments • A substance derived from killed infective pneumonia bacteria could transform (형질전환) noninfective living pneumonia bacteria to the infective type

  6. 그림 14.2

  7. Avery’s Experiments • Showed that DNA (not protein or RNA) was the molecule responsible for transforming pneumonia bacteria into the infective form

  8. Hershey and Chase’s Experiments • Showed that phage DNA (not protein) enters bacterial cells to direct the life cycle of the virus • Together, Griffith, Avery and coworkers, and Hershey and Chase established that DNA is the hereditary molecule

  9. 그림 14.3. DNA가 유전물질이라는 것을 보여주는 허시와 체이스의 실험.

  10. 14.2 DNA Structure • Watson and Crick brought together information from several sources to work out DNA structure • New model proposed that two polynucleotide chains wind into a DNA double helix

  11. Watson and Crick • Discovered that a DNA molecule consists of two polynucleotide chains twisted around each other into a right-handed double helix • Each nucleotide of the chains consists of • Deoxyribose • A phosphate group • A base (adenine, thymine, guanine, or cytosine)

  12. The Double Helix • Deoxyribose sugars are linked by phosphate groups to form a sugar–phosphate backbone (당-인산 골격) • Two strands are held together by base pairs • Adenine–Thymine, Guanine–Cytosine • Each full turn of double helix is 10 base pairs

  13. 그림 14.4. 4개의 뉴클레오티드로 구성된 DNA 폴리뉴클레오티드 사슬.

  14. 그림 14.5. DNA의 X-선 회절 분석.

  15. 그림 14.6. DNA 이중나선.

  16. 14.3 DNA Replication • Meselson and Stahl showed that DNA replication is semiconservative (반보존적) • DNA polymerases are the primary enzymes of DNA replication • Helicases unwind DNA to expose template strands for new DNA synthesis

  17. 14.3 (cont.) • RNA primers provide the starting point for DNA polymerase to begin synthesizing a new DNA chain • One new DNA strand is synthesized continuously; the other, discontinuously • Multiple enzymes coordinate their activities in DNA replication

  18. 14.3 (cont.) • Telomerases solve a specialized replication problem at the ends of linear DNA molecules • DNA replication begins at replication origins

  19. Semiconservative Replication • Two strands of parental DNA molecule unwind • Each is a template for the synthesis of a complementary copy

  20. 그림 14.7. 왓슨과 크릭의 DNA 복제 모형

  21. 그림 14.8. DNA 복제의 반보존적(a), 보존적(b), 분산적(c) 모형.

  22. 그림 14.9-1. 반보존적 모형을 증명하는 메셀슨과 스탈의 실험.

  23. 그림 14.9-2.

  24. 그림 14.10. DNA 중합효소가 5’→3’방향으로 상보적인 사슬을 만드는 반응.

  25. Two Antiparallel Strands • As DNA helix unwinds, one template strand runs in a direction allowing new DNA strand to be made continuously in the direction of unwinding • Other template strand is copied in short lengths that run in the direction opposite to unwinding • Discontinuous replication produces short lengths, then linked into a continuous strand

  26. 그림 14.11. 역평행인 주형가닥들은 분기점에서 어떻게 복제 되는가?

  27. Enzymes of DNA Replication • Helicase unwinds the DNA • Primase synthesizes RNA primer (starting point for nucleotide assembly by DNA polymerases) • DNA polymerases assemble nucleotides into a chain, remove primers, and fill resulting gaps • DNA ligase closes remaining single-chain nicks

  28. 그림 14.12-1. 헬리카제, 프리마제, DNA 중합효소, DNA 리가제 등의 활성을 포함하는 DNA 복제의 단계들.

  29. 그림 14.12-2.

  30. Telomeres • Ends of eukaryotic chromosomes • Short sequences repeated hundreds to thousands of times • Repeats protect against chromosome shortening during replication

  31. Telomerase • Chromosome shortening is prevented in some cell types which have a telomerase enzyme (adds telomere repeats to chromosome ends)

  32. 그림 14.13. 복제 과정 5’ 말단에서 프라이머가 제거되면 공백이 남게 됨.

  33. 그림 14.14. 진핵생물 염색체가 짧아지는 것을 방지하는 텔로미어 반복들.

  34. DNA Synthesis • Begins at sites that act as replication origins • Proceeds from the origins as two replication forks moving in opposite directions

  35. 그림 14.15. 진핵생물 염색체에서의 많은 복제 원점들.

  36. 14.4 Mechanisms That Correct Replication Errors • Proofreading (교정) depends on the ability of DNA polymerases to reverse and remove mismatched (불일치) bases • DNA repair (수선) corrects errors (오류들) that escape proofreading

  37. Proofreading • If a replication error causes a base to be mispaired, DNA polymerase reverses and removes the most recently added base • The enzyme then resumes DNA synthesis in the forward direction

  38. 그림 14.16. DNA 중합효소에 의한 교정.

  39. DNA Repair Mechanisms • DNA polymerase enzymes • Recognize distorted regions caused by mispaired base pairs • Remove DNA section with mispaired base from the newly synthesized nucleotide chain • Resynthesize the section correctly, using original template chain as a guide (길잡이)

  40. 그림 14.17. 복제된 DNA에서 불일치 염기들의 수선.

  41. 14.5 DNA Organization (체계; 조직)in Eukaryotes and Prokaryotes • Histones pack eukaryotic DNA at successive levels of organization • Many nonhistone proteins have key roles in the regulation of gene expression • DNA is organized more simply in prokaryotes than in eukaryotes

  42. Eukaryotic Chromosomes • Consist of DNA complexed with histone and nonhistone proteins • DNA wraps around a nucleosome (two molecules each of histones H2A, H2B, H3, H4) • Linker DNA connects adjacent nucleosomes • Binding of histone H1 causes nucleosomes to package into a coiled structure (solenoid) • Nonhistone proteins help control the expression of individual genes

  43. 그림 14.18. 진핵생물 염색질과 염색체에서의 조직화 단계.

  44. Chromatin • Distributed between: • Euchromatin (진정염색질)(loosely packed region, genes active in RNA transcription) • Heterochromatin (이질염색질)(densely packed masses, genes are inactive) • Folds and packs to form thick, rodlike chromosomes during nuclear division

  45. The Bacterial Chromosome • Closed, circular molecule of DNA packed into nucleoid (핵양체) region of cell • Replication begins from a single origin, proceeds in both directions • Plasmids (in many bacteria) replicate independently of the host chromosome

  46. Bacterial DNA • Organized into loops through interaction with proteins • Proteins similar to eukaryotic nonhistones regulate gene activity in prokaryotes

  47. 그림 14.19. 원핵생물의 원형 DNA에서 단일 원점으로부터의 복제.

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