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Structure & Function of DNA

Structure & Function of DNA. Understanding Growth & Development. 1. The Structure of DNA. DNA stands for: deoxyribonucleic acid DNA is: the molecule of life and is found in every organism DNA stores: information for proper cellular function. 2. The Structure of DNA, cont.

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Structure & Function of DNA

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  1. Structure & Function of DNA Understanding Growth & Development 1

  2. The Structure of DNA • DNA stands for: deoxyribonucleic acid • DNA is: the molecule of life and is found in every organism • DNA stores: information for proper cellular function 2

  3. The Structure of DNA, cont. • The complete DNA molecule is arranged in a structure called a double helix • Double helix – 2 coiled strands; twisted ladder

  4. The Structure of DNA, cont. • DNA is: a large polymer that contains the elements C,H,O,N & P • Polymer structure is made of single units (monomers) called nucleotides • 3 components of a nucleotide: • 5-carbon sugar • Phosphate group • Nitrogen-containing base

  5. The Structure of DNA, cont. • Sides of ladder: • Deoxyribose a 5-carbon (pentose) sugar • Phosphate group • Rungs of ladder: • 2 nitrogen-containing bases joined with 2 or 3 hydrogen bonds

  6. The Structure of DNA, cont. • Nitrogen Bases: • Cytosine - C • Guanine - G • Adenine - A • Thymine - T

  7. DNA Nucleotide Nitrogenous Base (A, G, C, or T) Phosphate Deoxyribose 7

  8. Nitrogen-containing Bases Double ring PURINES Adenine (A) Guanine (G) Single ring PYRIMIDINES Thymine (T) Cytosine (C) A or G T or C 8

  9. Base-Pairings • The DNA of all organisms follows the rule of base-pairing: Cytosine always bonds with Guanine and Adenine always bonds with Thymine

  10. Base-Pairings Three hydrogen bonds required to bond Guanine & Cytosine Two hydrogen bonds are required to bond Adenine & Thymine G C 10

  11. DNA 5 O 3 3 O P P 5 5 C O G 1 3 2 4 4 2 1 3 5 O P P T A 3 5 O O 5 P P 3 11

  12. Historical Landmarks in the Discovery of DNA 12

  13. 1868-Switzerland • Johann Friedrich Miescher • Found it when working with white blood cells that he took from pus drained out of a surgical wound.

  14. 1920-London • Frederick Griffith • Found that bacteria could acquire something from each other to turn harmless bacteria into deadly bacteria, though he wasn't sure what. 

  15. 1944-New York • Oswald Avery • Led a team that assessed Griffith’s work • Discovered the molecule DNA was what had caused the change.

  16. 1950-New York • Edwin Chargaff • Found that the amount of adenine was almost equal to the amount of thymine, and that the amount of guanine was almost equal to the amount of cytosine.  • Thus you could say: A=T, and G=C.  • This discovery later became Chargaff’s Rule. 

  17. 1952-London • Rosalind Franklin and Maurice Wilkins • Were able to obtain an x-ray image of crystalized DNA • It showed a ladder with rungs twisted in an “X” shape indicating DNA had a helix shape. 

  18. 1953-London • James Watson and Francis Crick • Published their findings about the structure of DNA • Watson, Crick and Wilkins received a Nobel Prize for their work in 1962

  19. All about you and your chromosomes • Humans- 46 chromosomes-23 pairs • 22 autosomal pairs or 44 body chromosomes • 1 pair of sex chromosomes-2 sex chromosomes • XX-girl XY- boys • X in eggs only • Sperm will have either an X or a Y

  20. DNA Replication DNA structure in : • Prokaryotes - single, circular piece; found in cytoplasm • Eukaryotes - arranged in multiple threads called chromosomes; found in nucleus

  21. DNA Replication, cont. • Number of chromosomes varies depending on organism: • Fruit Fly - 8 • Humans – 46 • Chimpanzees - 48 • Aquatic Rat - 92

  22. DNA Replication, cont. • Genes: sections of DNA on the chromosomes • Genes: code for certain proteins that provide instructions for cellular activity

  23. DNA Replication, cont. • Each cell of any type of organism must be able to make copies of its DNA to pass on to daughter cells • Replication – when DNA makes a copy of itself • Both strands of DNA are complementary to each other • Each serve as a template to make a new strand

  24. DNA Replication, cont. • DNA replication follows base-pairing rules and is carried out by a group of enzymes: • Some unwind DNA • Some break hydrogen bonds between bases • Some (DNA polymerase) add new bases to make new DNA strands

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