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DNA’s Discovery and Structure

DNA’s Discovery and Structure. Scientists that determined DNA’s Structure and Importance. 1866 Gregor Mendel – demonstrated that parents pass traits to offspring-thought traits contained in a molecule 1869 Friedrich Meisher – Isolated DNA from cell nucleus – named it nucleic acid

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DNA’s Discovery and Structure

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  1. DNA’s Discovery and Structure

  2. Scientists that determined DNA’s Structure and Importance • 1866 Gregor Mendel – demonstrated that parents pass traits to offspring-thought traits contained in a molecule • 1869 Friedrich Meisher – Isolated DNA from cell nucleus – named it nucleic acid • 1889 R.A. Altman-determined the chemical composition of DNA

  3. Scientists that Determined DNA’s Structure and Importance • 1919Phoebus Levene – Determined the structure of a DNA nucleotide – first to propose that DNA was a polymer made of nucleotides P= Phosphate S= 5C sugar B= Nitrogen base

  4. Scientists that Determined DNA’s Structure and Importance • @1928Frederick Griffith – bacterial transformation – traits passed by a chemical “transforming principle”@

  5. Scientists that Determined DNA’s Structure and Importance • 1944 Oswald Avery – DNA = key to transformation - Avery and his partners conducted experiments which proved that DNA was Griffith’s “transforming principle”

  6. Scientists that Determined DNA’s Structure and Importance • 1949 Erwin Chargaff – base-pairing rules %Adenine=%Thymine %Guanine=%Cytosine • 1952 Alfred Hershey & Martha Chase • Radioactive labeled Bacteriophage transformation experiment-settled DNA-protein debate

  7. Hershey & Chase

  8. Important Scientists in the “Race for the Double Helix” • 1952Maurice Wilkins & Rosalind Franklin • X-ray diffraction- “photographs” of DNA • DNA must be a some type of spiral (helix) • DNA’s diameter is constant and stable

  9. Important Scientists in the “Race for the Double Helix” • 1953 James Watson & Francis Crick • @Created the first accurate 3-D model of DNA@ • Won the Nobel Prize with Wilkins

  10. DNA’s Structure • DNA is composed of nucleotides • DNA contains four nitrogen bases: adenine(A) cytosine(C) guanine(G) thymine (T) • @A & G are purines C & T are pyrimidines@

  11. DNA’s Structure • DNA is a double helix -2 strands of DNA nucleotides joined to form a “twisted ladder” -the strands are held by hydrogen bonds between the nitrogen bases

  12. Chargaff’s Rule • The nitrogen bases form the “steps” on the DNA ladder by complementary pairing A == T C == G T == A G == C A == T@Aalways pairs with T T == ACalways pairs with G@ Sugar-phosphate backbone

  13. How the Code Works • The combination of A,T,G,C determines what traits you might have.. • C A T C A T = purple hair • T A C T A C = yellow hair

  14. How the Code Works • Think of the bases of DNA like letters • Letters form words… • Words form sentences..

  15. Central Dogma of Molecular Biology • 1958 Francis Crick proposed: @DNA codes for the production of RNA RNA codes forthe production of protein@ Protein does not code for the production of protein DNA or RNA “Once information has passed into protein it cannot get back out again”

  16. Who discovered the bacterial transformation? • Watson and Crick • Wilkins and Franklin • Griffith • Avery

  17. Who created the first 3D model of the double helix DNA? • Watson and Crick • Wilkins and Franklin • Griffith • Avery

  18. What is the complementary strand to C G T A • G C A T

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