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DNA

DNA. Module B: Bio . B.1. Describe the sculpture. Bio. B.1.2: Explain how genetic information is inherited. Bio.B.1.2.1-Describe how the process of DNA replication results in the transmission and/or conservation of genetic material. Before we get started…. What is genetics?

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DNA

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  1. DNA Module B: Bio . B.1

  2. Describe the sculpture

  3. Bio. B.1.2: Explain how genetic information is inherited • Bio.B.1.2.1-Describe how the process of DNA replication results in the transmission and/or conservation of genetic material.

  4. Before we get started… • What is genetics? • What is the genetic material?

  5. What molecule was the genetic material? • How did science identify what molecule is responsible for transmittance and conservation of the genetic material? • Three key experiments: • Griffith • Avery • Hershey and Chase

  6. GRIFFITHBacterial Transformation

  7. GRIFFITHBacterial Transformation • Transformation: process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria. • In Griffith’s experiment: one harmless form of bacteria was permanently transformed into the disease -causing bacteria.

  8. AVERYMolecular causes of transformation • Used Griffith’s experiment to determine the molecular basis of transformation. • He extracted molecules from heat killed bacteria. • What types of molecules did he extract? • Used enzymes to destroy proteins, lipids carbohydrates • Transformation still occurred • Used enzymes to destroy DNA • NO Transformation • What could we conclude from this result?

  9. AVERYMolecular causes of transformation • AVERY concluded… • DNA stores and transmits genetic information from one generation of bacteria to the next

  10. Transfer of DNA during transformation

  11. Hershey and ChaseThe role of bacterial viruses! • Bacteriophage: a virus that infects bacteria

  12. Hershey and ChaseThe role of bacterial viruses!

  13. Hershey and ChaseThe role of bacterial viruses! RESULTS • confirmed Avery’s results • Many scientists were now convinced that DNA is the genetic material found in genes in all living cells.

  14. The Role of DNA: • What is the role of DNA in heredity? • DNA must be capable of: 1. Storing information 2. Copying information 3. Transmitting information

  15. DNA stores information

  16. DNA copies and transmits information

  17. Quick Check • Which scientist first proposed that DNA is the genetic material • Which scientist used enzymes to confirm that DNA is the genetic material? • What is a bacteriophage? • What are the three functions of DNA?

  18. Section 12.2 Structure of DNA

  19. The Structure of DNA: • What are the chemical components of DNA? • Nucleotides are the building blocks of DNA • What are nucleotides composed of? 1. Phosphate 2. Sugar (deoxyribose) 3. Nitrogen Base • Adenine (A) • Guanine (G) • Cytosine (C) • Thymine (T)

  20. Nucleotides link together

  21. STRUCTURE of DNAChargaff: • Chargaff’s Rule: • percentages of A (adenine) and T(thymine) were equal in many sample of DNA • percentages of C (Cytosine) and G (Guanine) were also equal • It was concluded that A = T, and C= G • This was true for the DNA of many different types of organisms from bacteria to humans.

  22. STRUCTURE of DNAChargaff’s Data If a species has 35% adenine in its DNA, what is the percentage of the other three bases? Can you figure it out?

  23. STRUCTURE of DNARosalind Franklin • X-ray picture of DNA • DNA had two strands that twisted around each other like a coil

  24. STRUCTURE of DNAWatson and Crick • James Watson and Francis Crick built a three dimensional model of DNA • They determined that the shape of the DNA molecule was that of a double helix. • The double helix model explains Chargaff’s rule of base pairing and how the two strands of DNA are held together. Watson TED talk

  25. STRUCTURE of DNAWatson and Crick • The two strands of DNA run in opposite directions. • They are “antiparallel”. • This arrangement allows: • Nitrogen bases to join in the center of the molecule • Nucleotide sequences to be arranged like letters in a four-letter alphabet

  26. Antiparallel DNA Strands:

  27. Hydrogen bonding and base pairing: • The DNA strands are held together by hydrogen bonds that form between the nitrogen base pairs. • Nitrogen bases are paired according to Chargaff’s findings; • Adenine bonds to Thymine with two hydrogen bonds • Cytosine bonds with Guanine with three hydrogen bonds

  28. Section 12.3 DNA Replication

  29. What happens to the DNA structure during S phase? • DNA replicates (duplicates, is copied, etc.) • Watson and Crick’s 3D model immediately proposed a replication mechanism animation

  30. DNA Replication: • Occurs during interphase • Ensures that each resulting cell has the same complete set of DNA • Base pairing explains how DNA can be copied • Each strand has all the information needed to construct the other strand

  31. DNA Replication: 1. DNA is “unzipped” or separated • Enzyme = helicase • Breaks hydrogen bonds that hold the two strands of DNA together

  32. DNA Replication: • New strands are built • Enzyme = DNA polymerase • Joins individual nucleotides together to produce a new strand of DNA that is complementary to the other • Proofreads each new strand

  33. How is replication different in prokaryotes? • In eukaryotes, replication begins at many different locations and proceeds in both directions until each chromosome is completely copied • In prokaryotes, replication begins at one point and proceeds in two directions until the entire chromosome Is copied

  34. DNA Replication Prokaryotes Vs eukaryotes

  35. Quick Check 1 • The process by which one strain of bacterium is changed into another strain is called • Transcription • Transformation • Duplication • replication

  36. Quick Check • Bacteriophages are • A form of bacteria • Enzymes • Coils of DNA • viruses

  37. Quick Check 3. Which of the following researchers used radioactive markers in experiments to show that DNA was the genetic material in cells? Transformation • Griffith • Avery • Hershey and Chase • Watson and Crick

  38. Quick Check 4. Before DNA would definitively be shown to be the genetic material in cells, scientists had to show that it could • Tolerate high temperatures • Carry and make copies of information • Be modified in response to environmental conditions • Be broken down into smaller subunits

  39. Quick Check 5 5. A nucleotide does not contain • A 5-carbon sugar • An amino acid • A nitrogen base • A phosphate group

  40. Quick Check 6. According to Chargaff’s rule of base pairing which of the following is true about DNA? • A=T and C=G • A=C and T=G • A=G and T=C • A=T=G=C

  41. Quick Check 7. The bonds that hold the two strands of DNA together come from • The attraction of phosphate groups for each other • Strong bonds between nitrogenous bases and the sugar-phosphate backbone • Weak hydrogen bonds between bases • Carbon-to-carbon bonds in the sugar portion of the nucleotides

  42. Quick Check 8. In prokaryotes, DNA molecules are located in the • Nucleus • Ribosomes • Cytoplasm • histones

  43. Quick Check 9. In eukaryotes, nearly all the DNA is found in the • Nucleus • Ribosomes • Cytoplasm • histones

  44. Quick Check 10. The main enzyme involved in linking individual nucleotides into DNA molecules is • DNA protease • Ribose • Carbohydrate • DNA polymerase

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