Introduction to Molecular Biology

1. Introduction to Molecular Biology Fundamental Molecular Biology

2. Historical Background Classical Experiments Structure of nucleotides & DNA

3. What is Molecular Biology? Study of biological events at a molecular level The study of genes and gene activity at the molecular level

4. DNA History Discovered in 1869 by Friedrich Miescher as a component of nuclein By late 19th C. DNA & RNA are known to be polymers The function of these nucleic acids was not known

5. Early 20th C. Mendel’s genetics were rediscovered The concept of a ‘gene’ entered biology The question was “What makes up genes?” Three possibilities: DNA, RNA, or Proteins

6. Three sets of researchers provided the data that once and for all settled the question 1928: Fredrick Griffith experimented on transformation 1944: Oswald Avery, Colin MacLeod, & Maclyn McCarty repeated Griffith’s experiments, but added further biochemical tests 1952: A.D. Hershey & Martha Chase performed their experiment with bacteriophage

7. Griffith’s Transformation Experiment

8. Avery et al. repeated the experiment, but looked at each class of molecules to see their potential to transform

9. Hershey – Chase Experiment

10. Erwin Chargaff’s Data Allison, Fundamental Molecular Biology

11. Chargaff’s Rules How is information encoded within DNA Erwin Chargaff found that: [purine] = [pyrimidine] [Adenine] = [Thymidine] [Cytosine] = [Guanine]

12. DNA Structure

13. DNA X-Ray Diffraction Pattern Created By Rosiland Franklin Karp, Cell& Molecular Biology, 3E

14. Watson & Crick Model of DNA Double Helix http://salmon.psy.plym.ac.uk/year3/PSY339EvolutionaryPsychologyroots/watson-crick-dna.jpg

15. How does a helix of uniform pattern store information?

16. Nucleotide Structure

17. Sugars

18. Nitrogenous Bases

19. Phosphates

20. Glycosidic Bond

21. Base + Sugar = NUCLEOSIDE Base + Sugar + Phosphate = NUCLEOTIDE Essential Cell Biology, 2/e

22. Phosphodiester Linkage Allison, Fundamental Molecular Biology

24. DNA Structure

25. Watson-Crick Model of DNA Two chains of nucleotides form a right-handed helix Chains run in opposite directions Sugar-phosphate backbone is on the outside of the chains The paired bases are in planes nearly perpendicular to the long axis of the molecule (Base Stacking)‏ Hydrophobic interactions/Van Der Waal forces stabilize The two strands are held together by hydrogen bonds

26. 1.09 nm 0.34 nm 0.27 nm 0.6 nm 0.34 nm Allison, Fundamental Molecular Biology

27. Allison, Fundamental Molecular Biology

28. 2.0 nm 3.4 nm 0.34 nm -6° Tilt 34.3° Twist http://www.web.virginia.edu/Heidi/chapter12/chp12.htm

30. 3 Forms of DNA 2.4nm per turn 3.4nm per turn 4.6nm per turn 11bp per turn 10.5bp per turn 12bp per turn http://members.tripod.com/arnold_dion/RecDNA/Fig1-2.gif

31. http://chemistry.umeche.maine.edu/CHY431/Nucleic5.html

32. If the DNA is wound so that there are fewer bases per turn <9 bp, it is overwoundcreating positivesupercoiling The angle of twist increases from 34.3° to 37.7° If there are more bases per turn >11 bp, it is underwoundcreating negativesupercoiling The angle of twist decreases from 34.3° to 30.9° 30.9°< >37.7° 34.3° Essential Cell Biology, 2/e

33. E. coli genome negatively supercoiled http://www.cbs.dtu.dk/staff/dave/roanoke/genetics980213a.html

34. 11.1Å 10.8Å Allison, Fundamental Molecular Biology