DNA Chapter 2 – read principal points

1. DNA Chapter 2 – read principal points Timeline for genetics

2. Deoxyribonucleic acid • Functional Properties 1. Replication – DNA is copied prior to cell division why?

3. 2. Storage of information DNA inherited • from parent to offspring • from cell to cell • Gene expression – Genes encode proteins 3. Mutation – DNA changes to allow variation and adaptation, the basis of evolution

4. A six-legged green frog. (Reproduced by permission of JLM Visuals http://www.isogenic.info/assets/images/autogen/a_image16.jpg Neutral, harmful, adaptive? http://3quarksdaily.blogs.com/3quarksdaily/images/wolfe_seal_1.jpg

5. DNA History 1869 Meischer extracted nuclein from pus 1900s – chromosomes discovered The genetic material must have the 3 functional properties microscopy.bio.cmich.edu

6. Griffith finds “transforming factor”1928 London • Streptococcus pneumoniae bacterium • pneumonia in mice, deadly to humans sputum with bacteria

7. Smooth strain (IIIS) • virulent • polysaccharide capsule • capsule allows bacteria to evade immune system Fluorescent stain of capsule

8. isolate live IIIS • from mouse

9. S pneumococcus kills mouse in 24 hours. But 100 million IIR strain bacterial cells is harmless SR Appearance when grown on an agar plate (Research photographs of Dr. Harriet Ephrussi-Taylor, courtesy of The Rockefeller University.)

10. http://biology.kenyon.edu/courses/biol114/KH_lecture_images/How_DNA_works/how_DNA-works.htmlhttp://biology.kenyon.edu/courses/biol114/KH_lecture_images/How_DNA_works/how_DNA-works.html

11. Rough strain IIR is avirulent -> isolate live IIR IIR lacks capsule

12. The experiment: • Heat kill IIIS strain  mouse ?

13. Heat killed IIIS strain + live strain IIR  mouse ? Which strain is isolated?

15. Griffith’s experiment and conclusion A “transforming factor” in killed S strain transformed live R strain into S DNA or protein?

16. 1944 Avery, McCarty, Macleod 1. Heat kill IIIS 2. Remove lipids and sugars – how? FYI iGenetics: DNA as Genetic Material: Avery’s Transformation Experiment

17. 3. Divide into 3 and treat with: • protease • RNase • DNase  next, add live R cells to each

20. 1952 Hershey and Chase Used T2 bacteriophage + E. coli A phage is a virus that infects bacteria

21. How phage work 1. phage adsorbs onto bacterial surface 2. Genetic material injected 3. Cell makes progeny phage IS the genetic material DNA, or protein?

23. Experiment • Label phage protein with 35 S  infect E. coli  strip phage off cell surface • New phage are not radioactive

24. 2. Label phage DNA with 32 P -> infect E.coli -> blend -> • New phage contain 32 P

26. http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/pictures/hersheychase-experiment.htmlhttp://osulibrary.orst.edu/specialcollections/coll/pauling/dna/pictures/hersheychase-experiment.html

27. Hershey and Chase conclusion DNA is responsible for function and reproduction of phage virus = the genetic material

28. Structure of DNA = nucleotide polymers NUCLEOTIDES 1. Nitrogenous base • Purines = guanine and adenine G A How big IS a nucleotide? UTAH cell scale Purines attached to 1 carbon of sugar at 9 nitrogen, covalent bond, pyrimidines attached to 1 carbon at 1 nitrogen

29. Pyrimidines Thymine T Cytosine C • RNA contains uracil U

30. 2. Deoxyribose sugar RNA (ribose) 2’ OH makes RNA less stable than DNA Sugar + base = nucleoside

31. 3. Phosphate (PO4)Nucleotide= base + sugar + phosphate Phosphate covalently (phosphodietster bond) attached to 5’C of sugar Phosphodiester bond - Covalent bond between phosphate of one nucleotide and 3’ sugar carbon of another 9 N (purine) or 6N (pyrimidine) covalently bonded to 1C of sugar

32. DNA is a polymer of nucleotides polarity 5’carbon to 3’hydroxyl

33. DNA (double helix)Watson and Crick 1953 X-ray diffraction data Rosalind Franklin, Maurice Wilkins

34. DNA properties include:

35. Complementary base pairing 1. Hydrogen bonds between complementary bases How many bonds in a G-C pair? A-T? Which is stronger?

37. Complementary base pairs Which are the G-C pairs?

38. 2. antiparallel stands 5’  3’ and 3’  5’

39. 3. Sugar phosphate backbones

40. 4. Base composition DNA 50% purine 50% pyrimidine A = T G = C A/T = 1 C/G = 1 A +T does not equal C+G A + G = C + T Chargaff (1950)

41. 5. DNA can denature and renature • Melt hydrogen bonds (chemical or heat)

42. And 5. Right handed helix 6. Complete turn of the helix is 0.34 nm, 10 bases per turn 7. Major and minor grooves

43. Major and minor grooves

44. Forms of DNA B DNA right helix 10 bp/ turn A DNA right helix 10.9 bp/ turn Z DNA left helix 12 bp/turn (role?) Cellular DNA closest to B DNA 10.4 bp/turn

45. Replication of DNA by Complementary Base Pairing HHMI interactive DNA replication advanced

46. Organization of DNA in chromosomes • Genome • Full amount of genetic material in a single cell

47. Viral chromosome Single or double stranded DNA or RNA Circular or linear Influenza ssRNAHIV ssRNA Bacteriophage ds DNA Parvovirus ssDNA Herpes ds DNA

48. Genetic material in prokaryotes • 1 (usually) chromosome • Circular (most) chromosome • Supercoiled DNA located in nucleoid region Neisseria gonorrhoeae

49. E. coli = 4.6 million bp, circular chromosome 1500 um genome stuffed into a 1 um cell via supercoiling E. Coli cells E. coli DNA map of chromosome

50. Some bacteria contain extra-chromosomal DNA called a plasmid