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FINDING DNA National DNA DAY April 15, 2011 • National DNA Day commemorates the successful completion of the Human Genome Project in 2003 and the discovery of DNA's double helix by James Watson and Francis Crick in 1953. Proof of DNA as Genetic Material • Was the genetic material protein or DNA? • Mendel (peas) and Morgan (flies) did not know it was DNA. Did you know… • Every cell in your body has the same DNA (you got it from Dad and Mom). • The reason the cells look different is because different genes were turned on. Frederick Griffith • A medical officer was trying to find a vaccine against pneumococcus Rough and Smooth Pneumococcus Griffith 1920’s • Transformation Griffith’s Conclusion • harmless R cells (pneunomia) used the genetic information from the dead S cells and became harmful • = transformation = passing the inheritance factor from one organism to another Oswald Avery DNA • He had reported that , not protein (which was believed at the time), was the hereditary substance. Oswald Avery 1940’s Separated: RNA DNA Protein Caused S strain to cause pneumonia Simple centrifuge video Gave each to mice Alfred Hershey and Margaret Chase 1953 • Showed that the hereditary material in bacteriophage viruses is DNA. • McGraw Hill Ani Hershey-Chase Animations Hershey-Chase • CONCLUSION – • DNA is genetic material 32 because ( P) DNA 35 not ( S) protein guides viral replication Bacteriophages (“bacteria-eaters”) Mostly made of just protein coat and DNA Virus Examples • Cold Virus HIV Virus Bird Flu Virus Ebola Virus Herpes Virus Flu Attack! Bacteriophage Structure Bacteriophage killing bacteria Virus: Are they Alive? •Viruses can only replicate in a living host. pp. 480-1 Bacteriophage Lytic Infection 1.Attach to host 2. Insert DNA 3. Make and assemble DNA parts 4. Lyse (burst) Bacteriophage Infection Video Examples: •Cold •Flu Lysogenic Infection • BIOL 230 Lecture Guide - Lysogenic Life Cycle of a Temperate Bacteriophage (animation link) • 1. Virus lands on host. • 2. Virus injects DNA into host. • 3. Virus DNA attaches to host DNA = prophage. • 4. Virus Prophage will become lytic when conditions are favorable (you are sick, tired). Lysogenic Cycle Animation • EXAMPLES: HERPES HIV • GOOD ONE! McGraw Hill LyticLysogenic Animation • Herpicide-SWEET • Valtrex Click on “Journey into DNA” • NOVA Online | Cracking the Code of Life | Journey into DNA (keep clicking on “zoom” + button) What is the structure of DNA? • It is a nucleic acid • Polynucleotide = Made of long chains of Nucleotides DNA Nucleotide Phosphate Group O O=P-O O 5 CH2 O N C1 C4 Sugar (deoxyribose) C3 C2 Nitrogenous base (A, G, C, or T) DNA Structure • NUCLEOTIDE • POLYNUCLEOTIDE A Nucleotide • MADE OF: –Sugar –Phosphate –Base • Deoxyribose sugar • PO4 • 4 kinds: • (A) (G) (T) (C) (names on next slide) 4 Types of Base Pairs • A = adenine • T = thymine • C = cytosine • G = guanine • NOW SING THE DNA SONG Nitrogenous Bases • PURINES -2 rings 1. Adenine (A) 2. Guanine (G) A or G • PYRIMIDINES -1 ring 3. Thymine (T) 4. Cytosine (C) T or C DNA •Deoxyribonucleic Acid • (Get out colored pencils) DNA Double Helix “Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Phosphate & Sugar Backbone BONDS Covalent bonds join Phosphates and sugars H-bonds join N-bases DNA Structure • Rungs of the Ladder: – Various orders of A, T, C, G • Backbone: – Sugar and phosphates – Alternate DNA Double Helix 5 O 3 3 O P 5 O C G 1 P 5 3 2 4 4 2 3 1 P T 5 A P 3 O O P 5 O 3 5 P The other nucleic acid: RNA • Ribonucleic Acid Three types: – mRNA (messenger) – tRNA (transfer) – rRNA (ribosomal) THE RNA’s JOBS mRNA rRNA tRNA Takes code out of nucleus to ribosome Part of the Takes amino structure of acids to the ribosome ribosomes Comparing DNA and RNA • DNA • RNA • Double stranded • Sugar = deoxyribose • Bases: A-T, C-G • Found only in nucleus • Can repair itself • • • • Single stranded Sugar = ribose Bases: A-U, C-G Found in and out of the nucleus • Cannot repair itself RNA Making mRNA DNA Pretty Similar • Uracil • Thymine DNA - Contains Thymine - Contains deoxyribose sugar - Double stranded molecule - Found only in nucleus Both RNA - Made of nucleotides - Single stranded molecule - Contain adenine, guanine and cytosine - Contains uracil - Contains ribose sugar - Found in nucleus and cytoplasm • • • • • • • Relative Proportions (%) of Bases in DNA Organisms A T G C Human 30.9 Chicken 28.8 Grasshopper 29.3 Sea Urchin 32.8 Wheat 27.3 Yeast 31.3 E. coli 24.7 29.4 19.9 29.2 20.5 29.3 20.5 32.1 17.7 27.1 22.7 32.9 18.7 23.6 26.0 19.8 21.5 20.7 17.3 22.8 17.1 25.7 Question: • If there is 30% Adenine, how much Cytosine is present? • HINT: A –T and C - G Answer: • There would be 20% Cytosine. Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%) Total of 100% Chargaff’s Rules • the amount of (A)denine will always equal the amount of (T)hymine • And HOT!!! • the amount of (G)uanine will always equal the amount of (C)ytosine. Nitrogenous Bases • Why does A bond only with T and C only with G? • What do you notice? Nitrogenous Bases T and C are single-ring Pyrimidines A and G are double-ring Purines A single bonds with a double 2 chains of nucleotides bind to form a DNA molecule • Hydrogen bonds form between the nitrogenous bases to join the 2 chains together • The sugar and phosphate group together is known as the sugar-phosphate backbone ENZYMES FOR DNA REPLICATION • Helicase = separates 2 DNA strands (breaks H bonds) • Primase=RNA primers at INITIATION REPLICATION ENZYMES • Topoisomerase = unwinding DNA • DNA Polymerase = Adding of DNA nucleotides ELONGATION (proofread and repair) DNA REPLICATION ENZYMES • LIGASE= Binds the Okazaki fragments • Watch the enzymes in DNA Replication Animation AT and C-G Base Pairing • DNA Replication simple version) (link) • Media Showcase (cool animation link) • Detailed Replication Link DNA STRUCTURE • A-T • C-G • in tons of combinations makes our genetic code DNA Replication •Hi!...Still Awake? •DNA Replication Animation click here What is the complementary base sequence on the other strand of the DNA? A T T G C C C T A A • T A A C G G G A T T The Race is On! • To Determine the Structure of the DNA molecule. DNA Geek • Rosalind Franklin was an English chemist who was working in an X-ray crystallography lab in Paris, France in 1951. FAMOUS PHOTO 51 (correct orientation of DNAdouble helix) X ray Diffraction Franklin’s Suggestion DNA Geek Maurice Wilkins (1916-2004) • New Zealand Born British Scientist • It was his idea to study DNA by X-ray crystallographic techniques • Nobel Prize Linus Pauling • American biochemist suggested helix (spiral)shape • Most famous for Vitamin C prevents colds DNA Geek • Linus Pauling was a Caltech chemist (USA), who in 1951 had discovered the alpha helical nature of protein structure. I remember his books: Vitamin C and the Common Cold and Cancer and Vitamin C also The Nature of the Chemical Bond and protested nuclear testing DNA Geeks • James Watson, a biologist from Indiana University, and Francis Crick, a physicist, were working at the Cavendish Lab in Cambridge, England Nobel Prize for structure of DNA Francis Crick (1916-2004) Narrative - 8. Watson and Crick - Linus Pauling and the Race for DNA: A Documentary History • Born in England • Worked at Cambridge Crick’s first DNA sketch Worked on DNA structure with Watson James Watson (1928- ) • American age 22 • Ph.D. degree in Zoology in 1950 • Worked with Crick at the King’s College on the structure of DNA • At age 12 starred on QUIZ KIDS TV show • Recently at Cold Spring Harbor, NY, head of HGP Watson and Crick Met and worked at the Cavendish Laboratory Watson and Crick’s Wire Model DOUBLE HELIX First put the nitrogenous bases on the outside (incorrectly) DNA Bases Franklin corrects Watson and Crick • Told them their first model was incorrect • They had put the bases on the outside The Scandal • Watson used her pictures (Photo 51) to determine that DNA spirals into a double helix. • Little did Rosalind Franklin know that her laboratory colleague, Maurice Wilkins, was in the next room revealing months of her work to her competitor! Rosalind Franklin • Died of ovarian cancer at age 38 and so could not share in the Nobel Prize • Her work did lead the way to work on viruses • She was not included in the publication that reported the structure of DNA and she died before the Nobel Prize was given to Watson and Crick. Nobel Prize • In 1962 James Watson, Francis Crick, and Maurice Wilkins jointly received the Nobel Prize in medicine or physiology for their determination in 1953 of the structure of deoxyribonucleic acid (DNA). Violation of the Scientists' Code of Honor • It is necessary for scientists to share information with one another, for if they did not, science and knowledge would not develop and grow. However, the tacit agreement among scientists who use or borrow one another's findings is that proper credit must be given to the author or originator of the work. Beadle and Tatum’s Experiment • used X rays to cause mutations in strains of the mold Neurospora (a bread mold) • were able to create single gene mutations that incapacitated specific enzymes Beadle and Tatum The One Gene/One Enzyme Hypothesis Beadle and Tatum • Beadle and Tatum experiment animation EXPLAIN: •“The secret of life is complementarity.” Happy DNA DAY The day commemorates the completion of the Human Genome Project in April 2003, and the discovery of DNA's double helix. DNA Song NOVA | Ghost in Your Genes | PBS