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DNA: Deoxyribose Nucleic Acid The Genetic Material

DNA: Deoxyribose Nucleic Acid The Genetic Material. Introduction to DNA (PART 1) Ms. Kim Honors Biology. What does DNA stand for?. D eoxyribo n ucleic a cid. DNA. D eoxyribose n ucleic a cid  type of nucleic acid What is the other type of nucleic acid? RNA

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DNA: Deoxyribose Nucleic Acid The Genetic Material

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  1. DNA: Deoxyribose Nucleic AcidThe Genetic Material Introduction to DNA (PART 1) Ms. Kim Honors Biology

  2. What does DNA stand for? • Deoxyribonucleic acid

  3. DNA • Deoxyribosenucleic acid  type of nucleic acid • What is the other type of nucleic acid? • RNA • DNA function • to hold genetic code • Genetic code = genetic information/instructions for making proteins • DNA is found in nucleus of eukaryotic cells • Found in nucleoid region in prokaryotes

  4. What is DNA made of? • DNA is a macromolecule • Made up of nucleotides • Covalently and hydrogen bonded together • Double stranded • Helix • “Spiral”

  5. What is a nucleotide? • Molecule made of • Deoxyribose sugar • A phosphate group • A nitrogenous base

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

  7. Searching for Genetic Material • Gregor Mendel (1866): • discovered that inherited traits are determined by discrete units, or 'genes,’ - passed on from the parents. • Thomas Hunt Morgan (1910): • Discovered genes are located (linked) on chromosomes

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

  9. Griffith's Transformation Experiment • Used the Pneumococcusbacteria • Include2 types: • a virulent S strain with a Smooth coat • kills mice • a non-virulent R Rough strain • does not kill mice. • Heat destroys the harmfulness of S strain • When heated S is mixed with live R and injected into mice, the mouse dies. • WHY?

  10. Searching for Genetic Material http://brookings.k12.sd.us/biology/ch12DNARNA/Chapter%2012A.mpg

  11. 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)

  12. 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. • Noticed that: • # of Adenine = # of Thymine • # of Cytosine = # of Guanine • “Chargaff’s Rule”

  13. Chargaff's Rule (Data)

  14. Discovering the structure of DNA Chargaff’s Rules A = T C = G C and G are held more tightly together because they are connected by three hydrogen bonds, whereas A and T are held by only two. Chargaff movie and Building Blocks movie http://www.hhmi.org/biointeractive/dna/animations.html

  15. Discovering the structure of DNA Maurice Wilkins (1952) • Studied DNA using x-ray crystallography with another scientist named Rosalind Franklin • He showed Franklin’s x-ray photograph without Franklin’s consent to Watson and Crick, which helped them discover DNA’s structure. • Awarded the 1962 Nobel Prize for Physiology or Medicine with Watson and Crick

  16. 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

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

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

  19. How was the structure of DNA discovered? • 1953 – Watson and Crick • Wilkins shows Watson and Crick the x-ray pictures from Franklin • This information gave Watson & Crick the evidence to conclude DNA has a helical shape • Made model of DNA which was made up of two chains of nucleotides

  20. Discovering the structure of DNA • James Watson & Francis Crick (1953) • Discovered double helix structure • Solved the three-dimensional structure of the DNA molecule Watson Constructing Bair Pairs movie http://www.hhmi.org/biointeractive/dna/animations.html

  21. DNA Structure (PART 2) Ms. Kim Honors Biology

  22. DNA and Its Structure • From 1953

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

  24. DNA - basics • Deoxyribonucleic Acid • Stores and transmits genetic info • Tells the cells which proteins to make and when to make them • Made up of nucleotides • Phosphate group • Sugar • Nitrogen bases • Double helix structure

  25. The Structure of DNA • Made out of nucleotides • Includes a phosphate group, nitrogenous base and 5-carbon pentose sugar Nucleotide Structure 1 “link” in a DNA chain

  26. A Polynucleotide • MANY nucleotides (“links”) bonded together Nucleotide Structure DNA has a overall negative charge b/c of the PO4-3 (phosphate group)

  27. The Structure of DNA • Backbone = alternating P’s and sugar • Held together by COVALENT bonds (strong) • Inside of DNA molecule = nitrogen base pairs • Held together by HYDROGEN bonds (weaker) Backbone

  28. Phosphodiester Bond • The covalent that holds together the backbone • Found between P & deoxyribose sugar • STRONG!!!

  29. Minor Groove Major Groove

  30. 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

  31. Nitrogen Bases (2 types) • Purines (small word, big base) • Adenine • Guanine • Pyrimidines • (big word, small base) • Cytosine • Thymine • Chargaff’s rules • A=T, C=G • Hydrogen Bondsattractions between the stacked pairs; WEAK bonds

  32. Why Does a Purine Always Bind with A Pyrimidine?

  33. DNA Double Helix • 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… • Complementary strand:5’AATCGCTATAC3’ Template strand: 3’TTAGCGATATG5’

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