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DNA’s Discovery and Structure

Explore the fascinating world of DNA through its history, structure, and importance in protein synthesis. Learn about key scientists, genetic code, DNA replication, and the intriguing concept of genes.

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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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