DNA: Deoxyribose Nucleic Acid The Genetic Material Lecture #22A Ms. Day Honors Biology

DNA Deoxyribose nucleic acid  type of nucleic acid What is the other type of nucleic acid? RNA DNA function to hold genetic code Genetic code = genetic instructions to make proteins DNA is found in nucleus of eukaryotic cells Found in nucleoid region in prokaryotes

The Short History of DNA and Genetics (Part 1) From 1866-1953

Searching for Genetic Material Freidrich Miescher(1868): discovered DNA Isolated something new from the nuclei of eukaryotic cells Later called DNA!!!

Searching for Genetic Material Fredrick Griffith (1928): Studied effects of virulent (virus-causing) bacteria vs. nonvirulent bacteria injected into mice He used transformation: Inserted foreign DNA and changed protein/ trait believed that the transforming agent was an inheritance molecule

Non-virulent vs. Virulent Bacteria ROUGH: harmless SMOOTH: kill

NOT HARMFUL/BENIGN BAD/HARMFUL

Griffith's Transformation Experiment Used the Pneumococcus bacteria a virulent S strain with a Smooth coat kills mice a non-virulent R Rough strain does not kill mice. Heat destroys (kills) living cells!!! He heated smooth (harmful) cells So cells were DEAD! Then he mixed them with living Rough (benign) cells and injected into mice, BUT the mouse dies. WHY? http://www.quia.com/files/quia/users/hlrbiology/Animations/08_DNA_and_Proteins/Griffith_Mouse_Experiment.swf

Searching for Genetic Material

Searching for Genetic Material Oswald Avery, Colin MacLeod, & Maclyn McCarty (1944): Reported that “transforming agent” in Griffith's experiment was DNA Also used the Pneumococcus bacteria and test tubes (NOT mice)

So…DNA is the transforming agent!!

Discovering the Structure of DNA Edwin Chargaff (1950) Discovered a 1:1 ratio of adenine to thymine and guanine to cytosine in DNA samples from a variety of organisms.

Relative Proportions (%) of Bases in DNA Chargaff's Rule (Data) Relative Proportions (%) of Bases in DNA ORGANISM A T G C Human 30.9 29.4 19.9 19.8 Chicken 28.8 29.2 20.5 21.5 Grasshopper 29.3 20.7  Sea Urchin 32.8 32.1 17.7 17.3 Wheat 27.3 27.1 22.7 22.8 Yeast 31.3 32.9 18.7 17.1 E. coli 24.7 23.6 26.0 25.7

Discovering the Structure of DNA Chargaff’s Rules A = T C = G

Discovering the structure of DNA Maurice Wilkins (1952) Photographed DNA using x-ray crystallography Worked with another scientists named Rosalind Franklin Awarded the 1962 Nobel Prize for Physiology or Medicine with Watson and Crick

 X-rays passing through a helix diffract at angles perpendicular to helix making an "X" pattern, which favors an equal diameter "helix".

Discovering the structure of DNA Photo 51 Rosalind Franklin (1952) Obtained sharp X-ray diffraction photographs of DNA (Photo 51) Watson and Crick used her data  revealed its helical shape Watson and Crick went on to win Nobel Prize (1962) for their DNA model

She finally gets credit  Rosalind Franklin University of Medicine and Science, located on Green Bay Road in North Chicago, Illinois

Searching for Genetic Material Alfred Hershey & Martha Chase (1952) Confirmed DNA IS genetic material Used bacteriophages (viruses) HYPOTHESIZED DNA, not protein, is the hereditary material

Searching for Genetic Material Hershey and Chase Experiment Animation http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html

Searching for Genetic Material Hershey and Chase Experiment

Discovering the structure of DNA James Watson & Francis Crick (1953) Discovered double helix structure Solved the three-dimensional structure of the DNA molecule

Ms. Gaynor Honors Biology DNA’s Structure Lecture #22B Ms. Gaynor Honors Biology

DNA and Its Structure (Part 2) From 1953

Recall… DNA and RNA are nucleic acids An important macromolecule in organisms that stores and carries genetic information

What is the Double Helix? Shape of DNA Looks like a twisted ladder 2 coils are twisted around each other Double means 2 Helix means coil

1 “link” or monomer in a DNA chain The Structure of DNA Made out of nucleotides MONOMERS of nucleic acids Includes: phosphate group (PO4-3) nitrogenous base and 5-carbon pentose sugar 1 “link” or monomer in a DNA chain

DNA has a overall negative charge b/c of the PO4-3 (phosphate group) 2 Polynucleotides MANY nucleotides (“links”) bonded together DNA has a overall negative charge b/c of the PO4-3 (phosphate group)

The Structure of DNA Backbone Backbone = alternating PO4-3 & sugar Held together by COVALENT bonds (strong) Inside of DNA molecule = nitrogen base pairs Held together by HYDROGEN bonds (weaker) Backbone

The covalent that holds together the backbone Phosphodiester Bond The covalent that holds together the backbone Found between PO4-3 & deoxyribose sugar of 2 DIFFERENT nucleotides STRONG!!!

DNA is antiparallel Antiparallel means that the 1st strand runs in a 5’ 3’ direction and the 2nd 3’ 5’ direction THEY RUN IN OPPOSITE or ANTIPARALLEL DIRECTIONS P end is 5’ end (think: “fa” sound) -OH on deoxyribose sugar is 3’ end 5’ and 3’ refers to the carbon # on the pentose sugar that P or OH is attached to

DNA in Cells 2 broad categories of cells 1. Eukaryotic cells: have nucleus with DNA DNA is contained in structure called a chromosome Chromosomes are a LINEAR (line) shape with ENDS called telomeres (protective “caps”) 2. Prokaryotic cells: no nucleus (nucleoid region instead) which contains DNA DNA is a CIRCULAR shaped chromosome without ENDS (no telomeres)

DNA Bonding Purines (small word, big base) Pyrimidines Adenine Guanine Pyrimidines (big word, small base) Cytosine Thymine Chargaff’s rules A=T, C=G Hydrogen Bonds attractions between the stacked pairs; WEAK bonds

Why Does a Purine Always Bind with A Pyrimidine?

DNA Double Helix LET’S PRACTICE… http://www.sumanasinc.com/webcontent/animations/content/DNA_structure.html Watson & Crick said that… strands are complementary nucleotides line up on template according to base pair rules (Chargaff’s rules) A to T and C to G LET’S PRACTICE… Template: 5’ AATCGCTATAC3’ Complementary strand: 3’ TTAGCGATATG5’