1 / 21

Discovering the Structure of DNA

Discovering the Structure of DNA. What is DNA?. DNA = deoxyribonucleic acid Stores, transmits and copy all information Located in the cell’s nucleus. What do you know about DNA?. Codes for proteins nucleic acid Monomer is a nucleotide The three parts of a nucleotide:

marny-cook
Télécharger la présentation

Discovering the Structure of DNA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Discovering the Structureof DNA

  2. What is DNA? • DNA = deoxyribonucleic acid • Stores, transmits and copy all information • Located in the cell’s nucleus

  3. What do you know about DNA? • Codes for proteins • nucleic acid • Monomer is a nucleotide • The three parts of a nucleotide: • 1. Phosphate group • 2. Sugar (deoxyribose) • 3. Nitrogen base

  4. Nitrogen bases • nitrogen two types: purine- 2 carbon rings pyrimidine. -1 carbon ring

  5. More about nitrogen bases • DNA has 4 nitrogen bases: • Thymine (T) • Adenine (A) • Cytosine (C) • Guanine (G) • A G - purines • C T - pyrimidines.

  6. YouTube: DNA Structure of DNA

  7. A collaborative effort! • Early 1900s • known: information is passed from cell to cell. • Unknown: what carried the information? • scientists thought a protein • others that it was a nucleic acid. • Three major experiments helped shows nucleic acid carried cell information: • Griffith • Avery • Hershey-Chase

  8. Frederick Griffith • studied pneumonia bacteria • 1928 • isolated two strains of pneumonia • injected them into mice

  9. Griffith got lucky? • Something transferred from heat-killed bacteria • What happened? • Griffith’s conclusions: • Transformation = process by which one strain of bacteria changes the gene(s) of another bacteria

  10. Avery • DNA was transforming bacteria • 1943 • Uses pneumonia ( just like Griffith) • Showed gene is made of DNA • Scientists were slow to accept the results

  11. Hershey and Chase • bacteriophages to see if information is carried on proteins or DNA • 1950 • Further supported Avery’s experiment that genetic material is DNA http://www.accessexcellence.org/RC/VL/GG/images/HERSHEY.gif

  12. Discovery of the structure of DNA • Many scientists contributed to determining the structure of DNA • Erwin Chargaff • Rosalind Franklin • James Watson & Francis Crick

  13. Erwin Chargaff • Base pairing rule • 1950 • percentages of bases in DNA • 10% A = 10% T • 40% C = 40% G • This is Chargaff’s Rule!

  14. Rosalind Franklin • x-ray photography to try to find DNA structure • 1952 • Her “Photo 51” revealed DNA’s structure • Died of cancer in 1958

  15. Watson and Crick http://teachers.sduhsd.k12.ca.us/lolson/images/watson_crickjpg • Credited with finding the structure of DNA) • 1953 • Watson got a sneak peak at Franklin’s x-ray photos and used them with other evidence • Did not give credit to Franklin

  16. DNA structure • Twisted ladder • made of nucleotides • Sides- phosphate/sugar • Rung- nitrogen bases

  17. What bonds with what? • A bonds with T • G bonds with C • Bonds sides- covalent- strong rungs - hydrogen - weak

  18. Your turn...the structure of DNA Sugar /P backbone Sugar /P backbone Base pair • On the diagram: • Circle and label a nucleotide. • Label the sugar and phosphate molecules. • Label the bases • Label a base pair. • Label the sugar-phosphate backbones. • Label the hydrogen bonds. A Hydrogen bonds C G P A T S T A C G G nucleotide

More Related