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DNA’s Discovery and Structure

DNA’s Discovery and Structure. Honors Objectives SOL.BIO.6f. Today’s Objectives:. TSW investigate and understand the common mechanisms of protein synthesis, including the structure of DNA and its discovery. Our Genetic Code.

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DNA’s Discovery and Structure

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  1. DNA’s Discovery and Structure Honors Objectives SOL.BIO.6f

  2. Today’s Objectives: • TSW investigate and understand the common mechanisms of protein synthesis, including the structure of DNA and its discovery.

  3. Our Genetic Code • The genetic code is a sequence of nucleotides in the __________ of eukaryotic cells. • There are two polymers of nucleic acids, _____ and ______.

  4. Important Scientists that determined DNA’s Importance • Frederick Griffith – bacterial transformation • Oswald Avery – DNA = key to transformation • Alfred Hershey & Martha Chase • Bacteriophage transformation experiment • Erwin Chargaff – base-pairing rules

  5. Important Scientists in the “Race for the Double Helix” • Maurice Wilkins & Rosalind Franklin • X-ray diffraction • DNA must be a some type of spiral (helix) • DNA’s diameter is constant and stable • James Watson & Francis Crick • Created the first accurate model of DNA • Won the Nobel Prize

  6. DNA’s Structure • DNA is a double helix • DNA contains four nucleotide bases: • adenine (A) • cytosine (C) • guanine (G) • thymine (T)

  7. Chargaff’s Rule • The bases form the “rungs” on the DNA ladder by complementary pairing A == T C == G T == A G == C A == T T == A Sugar-phosphate backbone

  8. DNA Replication • Replication = Duplication • Happens in the S phase of Interphase • Must replicate before mitosis or meiosis I • Part of the double helix is unwound • Replication in small pieces (Okazaki fragments) • Enzyme stitches pieces together later

  9. Semi-Conservative Replication • One-half of each new molecule of DNA is old (template strand) • One-half of new molecule of DNA is new (complementary strand)

  10. What is a Gene? • A length of DNA on a chromosome • May be in several parts • Exon – the expressed parts of the DNA sequence • Intron – the intervening, “junk DNA”, not expressed • Parts are cut, put together and then used to make RNA and proteins

  11. Odd Types of Genes • Multigene families • Transposons (Barbara McClintock) • Protective Genes • Viruses may give us new DNA that can be kept over time to cause new evolutionary changes!

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