1. DNA: History & Structure 1871 – Meischer - Nuclein 1879 – Flemming - Chromatin 1884 – Kossel – nuclei acids (four bases) 1928 – Griffith “transfomation” 1944 – Avery 1952 – Hershey Chase 1902 – Boverii – Sutton Chromosome Theory 1915 – Thomas Morgan Hunt 1948 – Pauling – alpha helix proteins 1950 - Chargaff – Base Pairing Rule 1953- Watson and Crick DNA double helix To be continued … … next unit

2. DNA History Objectives Understand and appreciate the development of scientific knowledge is an ongoing complex combination of various scientific discoveries. Evaluate the importance and relevance of various discoveries in history to current understanding of the structure and function of DNA. Explain how Griffith and Avery’s experiment and data influenced the idea that DNA might be responsible for inherited traits. Explain how the experiment and data from Hershey-Chase experiment proved DNA was the genetic material (not proteins). Explain how information from X-ray Crystallography photo 51 could lead to understanding the structure of DNA molecules.

3. Explain how Griffith, Avery, and Hershey-Chase experiments resulted in understanding that DNA is responsible for inherited traits. Frederick Griffith Bacteriologist studying pneumonia Discovered two types of bacteria: smooth and rough Smooth caused disease When heat killed smooth bacteria were mixed with live rough – a “transformation” occurred resulting in the rough bacteria producing smooth and being disease causing. Oswald Avery Continued Griffith’s experiment adding specific “destroying enzymes” to the heat killed smooth bacteria. Enzymes used destroyed: Carbohydrates, Lipids, Proteins, DNA, or RNA. Results showed all samples were disease causing except those from the heat killed smooth bacteria with DNA destroying enzyme – DNA must be cause for “Transformation of heritable material” Hershey & Chase Used a different method to prove Griffith and Avery correct – DNA is the genetic material Blender experiment Used bacteriophage (virus) to show that the protein coat is not present inside infected E. coli cells, whereas, DNA is – DNA is the genetic material.

4. Explain Griffith’s experimental design including how his data lead to his conclusion. Explain how it is possible for the mouse injected with the mixture of heat killed S bacteria and live R bacteria to die due to S strain bacterial pneumonia.

5. Explain Avery’s experimental design including how his data lead to his conclusion. Using the data from the experiment, explain how Avery and his team could conclude that DNA was the transforming factor.

6. Explain how the experiment and data from Hershey-Chase experiment proved DNA was the genetic material (not proteins). Which molecule is responsible for passing heritable information from generation to generation? Alfred Hershey & Martha Chase devised an experiment to determine if it was protein or DNA which was the genetic material in viruses. Alfred Hershey & Martha Chase Protein?DNA?

7. Question Which part of the Virus contains the genetic information? Setup One type of radioactive isotopes was used to label T2 Bacteriophages Protein Coat – Sulfur (S-35) or DNA – Phosphorus (P-32) Labeled T2 Bacteriophage infect E. coli cells and reproduce Centrifuge mixture to separate virus and bacteria Virus in supernatant (liquid) verses Bacteria forms a pellet Data Experimental data found Experiment using S-35: Radioisotopes found only in supernatant Experiment using P-32: Radioisotopes found only in the pellet Conclusion Molecule containing phosphorus labeled isotope was passed from one generation to the next when viruses reproduce though infecting bacteria; therefore the DNA must be the genetic molecule

8. Composition of Deoxyribonucleic Acid Macromolecule Nucleic Acid polymer made of repeated monomer units called nucleotides joined by covalent bonds Nucleotide monomer Phosphate group forms phosphodiester linkages (bonds) 5 carbon sugar (pentose) Nitrogen containing base (purine or pyrimidine)

10. Double helix 2 anti-parallel strands joined by hydrogen bonds Slightly Acidic has a negative charge due to ability to donate H + Phosphate groups are negative charged

11. Basic information about the structure of DNA

12. Why did the structure of DNA need to be figured out? DNA was found to be the molecule responsible for storing information & passing this information on to future generations. The way in which the information is expressed, copied and passed from one generation to the next could not be understood until the structure of the DNA molecule itself was figured out. With the knowledge of DNA’s structural composition; mutations, gene expression and molecule replication could be explained.

13. When studying the % composition of Nitrogen Bases in various organisms; The % composition in organisms of A, T, G, C varies… yet The T & A are always similar and the C & G are always similar Discovered proteins have alpha helical shapes X-ray crystallography photos of DNA Used models to formulate an accurate description of the structural nature of the DNA molecule.

14. Chargaff’s Base Pairing Rule

21. DNA Test Friday History Meischer, Griffith, Avery, Hershey-Chase, Franklin, Chargaff, Wilkins, Pauling, Watson & Crick, Meselson-Stahl Structure Nucleotide, purine vs pyrimidine, Replication Label diagrams, enzymes name-function, Packing How is DNA packed? Histones, nucleosomes, solenoid chromatid, centromere, chromosomes

22. DNA Replication is required to ensure identical genetic information in new cells DNA replication occurs during the s phase of the cell cycle DNA replication is required prior to somatic cell and gamete cell production

23. DNA replication is semi-conservative and depends on complimentary base pairing Meselson & Stahl experiment determined that DNA replication was semiconservative Chargaff’s base pairing ensures all DNA strands are identical

24. All starting DNA is produced in N-15 (heavy) After one generation of replication in N-14 (light) ALL DNA was found to be medium in weight and therefore composed of one light strand and one heavy strand = semi- conservative…. Meselson & Stahl experimental procedure, data, data analysis & conclusion Meselson and Stahl Experiment

25. Replication occurs in the 5’  3’ direction only Leading strand = continuous Lagging strand = discontinuous has Okazaki fragments DNA Replication occurs differently on each strand due to antiparallel nature of DNA

26. DNA Replication is carried out by a complex system of enzymes Proteins & Enzymes: 1)Helicase 2)Gyrase (Topoisomerase) 3)Primase 4)Ligase 5)Polymerase 6)SSB (single stranded binding proteins)

28. Lagging strand Helicase breaks H bonds and expose nitrogen bases. Primase adds and RNA primer DNA polymerase adds nucleotides in a 5’  3’ direction creating Okazaki fragments Gap between fragments are closed by DNA ligase

29. Nucleotide polymerization = dehydration synthesis Nucleotides are added one at a time in the form of “deoxynucleoside triphosphates”. Two phosphates are released from each nucleotide and the energy from dephosporylation is used to join nucleotides in a growing DNA chain.

30. 3 meters of DNA squished into 20 micron nucleus. DNA needs to be organized in a way to allow for specific gene expression and DNA replication

31. Nucleosome = histone proteins with DNA wrapped around

32. Packing and Supercoiling DNA

33. ss

34. Genes & Gene expression