Do Now 4

1. Do Now 4 • Write everything you know about DNA. • Write something that you kind of know, or have heard, about DNA. • Write something you would like to know, or think your about to learn, about DNA.

2. DNA Chapter 10

3. Essential Question: How do we know DNA makes up our genetic material? • Griffith: Pneumonia strains & Transformation • Oswald Avery: Process of elimination. • Used enzymes to destroy components of bacterial strains. Transformationoccurred in the absence of all macromolecules, exceptDNA. • Hershey & Chase: Bacteriophages • By using radioactiveisotopes, it was discovered that DNA is the genetic material of viruses.

4. EQ: How do we know DNA makes up our genetic material? Griffith • Transformation: One strain of bacteria was permanently genetically altered.

5. EQ: How do we know DNA makes up our genetic material? Oswald avery • I’m thinking of a number between 1 & 5. • 1 • 2 • 3 • 4 • 5 • Proteins • Carbs • Lipids • DNA • Other molecues

6. EQ: How do we know DNA makes up our genetic material? 0 Head DNA Tail Tail fiber

7. EQ: How do we know DNA makes up our genetic material? 0 Phage injects DNA. Phage DNA directs host cell to make more phage DNA and protein parts. New phages assemble. Phage attaches to bacterial cell. Cell lyses and releases new phages.

8. EQ: How do we know DNA makes up our genetic material? DNA Replication animations • dna replication fork - http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

9. “Review” • What 3 experiments led us to know that DNA makes up genetic information? • What is the purpose of DNA? • What do you remember about the structure of chromosomes?

10. EQ: What is the overall structure of DNA? The Components and Structure of DNA • What is the overall structure of the DNA molecule?

11. DNA is a type of Nucleic Acid • Nucleic acids are long, slightly acidic molecules originally identified in cell nuclei. • Nucleic acids are made up of nucleotides, linked together to form long chains.

12. EQ: What is the overall structure of DNA? The Components and Structure of DNA • The Components and Structure of DNA • DNA is made up of nucleotides. • A nucleotide is a monomer (single molecule) of nucleic acids made up of • A five-carbon sugar called deoxyribose • aphosphategroup • & one of fournitrogenousbases.

13. EQ: What is the overall structure of DNA? The Components and Structure of DNA • The nucleotides in a strand of DNA are joined by covalent bonds formed between their sugar and phosphate groups. Covalent bonds

14. EQ: What is the overall structure of DNA? The Components and Structure of DNA • There are four kinds of nitrogen bases in DNA: • adenine • guanine • cytosine • thymine

15. 1.) Adenines & Guanines belong to a class of nitrogenous base known as ________. • 2.) Cytosines and Thymines belong to a class of nitrogenous base known as ______. Double Ring Structures Single Ring Structures

16. EQ: What is the overall structure of DNA? The Components and Structure of DNA • The backbone of a DNA chain is formed by sugar and phosphate groups of each nucleotide. • The nucleotides can be joined together in any order.

17. EC: What led to the discovery of the structure of DNA? • EC: What led to the discovery of the structure of DNA?

18. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? The Components and Structure of DNA • Chargaff's Rules • Erwin Chargaff discovered that: • The percentages of guanine [G] and cytosine [C] bases are almost equal in any sample of DNA. • The percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA.

19. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? The Components and Structure of DNA • Chargaff's Rules • Erwin Chargaff discovered that: • For every guaninethere is a cytosine [G] = [C] • For every adeninethere is a thymine [A] = [T]

20. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? The Components and Structure of DNA Franklin’s X-Ray Evidence  • In the 1950’s Rosalind Franklin used X-ray diffraction to get information about the structure of DNA.

21. EC: What led to the discovery of the structure of DNA? • X-ray diffraction revealed an X-shaped pattern showing that the strands in DNA are twisted around each other like the coils of a spring. • Suggested two strands in the structure. • Suggested that the nitrogenous bases are near the center of the DNA molecule.

22. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? The Components and Structure of DNA • The Double Helix  • Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other like a twisted ladder.

23. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? • 2 sugar-phosphate “backbones” make up the two sides of the twisting ladder. • The third component of the nucleotide, the nitrogenous bases, make up the rungs (steps) of the ladder.

24. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? The Components and Structure of DNA • In the double-helix model, the two strands of DNA are “antiparallel”—they run in opposite directions. • Enables the nitrogenousbases on both strands to come into contact at the center of the molecule.

25. Anti-parallel strands • Nucleotides in DNA backbone are bonded from phosphate to sugar between 3 & 5 carbons • DNA molecule has “direction” • complementary strand runs in opposite direction 5 3 3 5

26. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? 5’ 3’ • DNA Double Helix 5’ 3’

27. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? The Components and Structure of DNA • Watson and Crick discovered that hydrogen bonds can form between certain nitrogenousbase pairs. • This principle is called base pairing. • Hydrogen Bonds hold the rungs of the latter together.

28. EC: What led to the discovery of the structure of DNA? EQ: What is the overall structure of DNA? • Base pairing explained Chargaff’srule: why… [A] = [T] and [G] = [C]. • For every adenine in a double-stranded DNA molecule, there had to be exactly one thymine. For each cytosine, there was one guanine. 3’ 5’ 5’ 3’

29. Review: The Components and Structure of DNA EQ: What is the overall structure of DNA? • DNA is made up of nucleotides that consist of a 5 carbon deoxyribose sugar, a phosphate group, and 1 of 4 nitrogenousbases • DNA is takes a double helix shape, like a twisted ladder. Two sugar-phosphate backbones, which are held together by covalentbonds make up the sides of the twisted ladder while nitrogenous bases, held together by hydrogen bonds make up the rungs, or connect in the center. • The strands of the double helix run antiparallel, which allows them to link up as exact opposites. • Nitrogenous bases form hydrogen bonds with their base pair A-T, C-G.

30. Review: The Components and Structure of DNA EQ: What led to the discovery of the structure of DNA? • Chargoff determined that, in a double-stranded DNA molecule, adenine & thymine are present in equal proportions, as are guanine and cytosine. • Franklins X-Ray revealed the spiral structure of DNA. • Both contributed to Watson & Crick’s understanding of DNA’sdoublehelix and complementarybasepairing, which led to their double helix model of DNA.

31. Do Now 5 • Summarize the roles of Griffith, Avery, & Hershey & Chase in determining that DNA contains our genetic material. • What did Chargaff, Franklin, & Watson & Crick contribute to understanding the structure of DNA.

32. Chapter 10.4 DNA replication

33. Double helix structure of DNA “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” Watson & Crick

35. Base pairing in DNA • Purines • adenine (A) • guanine (G) • Pyrimidines • thymine (T) • cytosine (C) • Pairing • A : T • 2 bonds • C : G • 3 bonds

36. Copying DNA • Replication of DNA • base pairing allows each strand to serve as a template for a new strand • new strand is 1/2 parent template & 1/2 new DNA

37. DNA Replication • Large team of enzymes coordinates replication

38. Replication: step 1: DNA Unwinds • Unwind DNA • helicaseenzyme • unwinds part of DNA helix • stabilized by single-stranded binding proteins helicase single-stranded binding proteins replication fork

39. Replication: step 2 Adding Complementary Nucleotides • Build daughter DNA strand • add new complementary bases • Uses DNA polymerase III Where’s theENERGYfor the bonding! DNA Polymerase III

40. Energy of Replication Modified nucleotides comewith their ownenergy! Where does energy for bonding usually come from? energy YourememberATP!Are there other waysto get energyout of it? energy Are thereother energynucleotides?You bet! And we are left with anucleotide! CTP ATP TTP GTP AMP ADP GMP TMP CMP modified nucleotide

41. Energy of Replication • The nucleotides arrive as nucleosides • DNA bases with P–P–P • P-P-P = energy for bonding • DNA bases arrive with their own energysource for bonding • bonded by enzyme: DNA polymerase III ATP GTP TTP CTP

42. Replication 3 5 energy DNA Polymerase III • Adding bases • can only add nucleotides to 3 endof a growing DNA strand • need a “starter” nucleotide to bond to • strand only grows 53 DNA Polymerase III energy DNA Polymerase III energy DNA Polymerase III energy 3 5

43. ligase 5 3 5 3 need “primer” bases to add on to energy  no energy to bond energy energy energy energy energy energy 3 5 3 5

44. Okazaki ligase 3 3 3 3 3 3 3 5 5 5 5 5 5 5 Leading & Lagging strands Limits of DNA polymerase III • can only build onto 3 end of an existing DNA strand  Okazaki fragments Lagging strand growing replication fork  Leading strand Lagging strand • Okazaki fragments • joined by ligase • “spot welder” enzyme DNA polymerase III Leading strand • continuous synthesis

45. DNA polymerase III 3 3 3 3 3 3 3 3 3 3 3 growing replication fork growing replication fork 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Replication fork / Replication bubble leading strand lagging strand leading strand lagging strand leading strand lagging strand

46. 3 3 3 3 3 3 DNA polymerase III 5 5 5 5 5 5 Starting DNA synthesis: RNA primers Limits of DNA polymerase III • can only build onto 3 end of an existing DNA strand growing replication fork primase RNA RNA primer • built by primase • serves as starter sequence for DNA polymerase III

47. ligase 3 3 3 3 5 5 5 5 Replacing RNA primers with DNA DNA polymerase I • removes sections of RNA primer and replaces with DNA nucleotides DNA polymerase I growing replication fork RNA But DNA polymerase I still can only build onto 3 end of an existing DNA strand

48. direction of replication Replication fork DNA polymerase III lagging strand DNA polymerase I 3’ primase Okazaki fragments 5’ 5’ ligase SSB 3’ 5’ 3’ Helicase` DNA polymerase III 5’ leading strand 3’ SSB = single-stranded binding proteins

49. DNA Replication EQ: How can DNA replicate? Telomeres • The tips of chromosomes are known as telomeres. • The ends of DNA molecules, located at the telomeres, are difficult to copy. • Over time, DNA may be lost from telomeres each time a chromosome is replicated. • What potential problem could this cause?

50. DNA Replication EQ: How can DNA replicate? Telomeres • An enzyme called telomerase compensates for this problem by adding short, repeated DNA sequences to telomeres, lengthening the chromosomes slightly and making it less likely that important gene sequences will be lostfrom the telomeres during replication.