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DNA Discovery & Structure: Milestones & Significance

Unravel the fascinating journey of DNA discovery and structure by prominent scientists, from Mendel to Watson-Crick's double helix model. Learn about the importance of DNA and its composition of nucleotides and nitrogen bases. Understand key concepts like Chargaff's Rule, genetic coding, and the Central Dogma of Molecular Biology. Delve into pivotal experiments such as bacterial transformation and X-ray diffraction, shaping our understanding of DNA's intricate nature.

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DNA Discovery & Structure: Milestones & Significance

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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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