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Chapter 10

Chapter 10. DNA. 10.1 Discovery of DNA. Griffith’s Experiments (1928) Griffith’s experiments showed that hereditary material can pass from one bacterial cell to another.

jaquelyn-knowles
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Chapter 10

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  1. Chapter 10 DNA

  2. 10.1 Discovery of DNA • Griffith’s Experiments (1928) • Griffith’s experiments showed that hereditary material can pass from one bacterial cell to another. • The transfer of genetic material to one cell from another cell or from one organism to another organism is called transformation.

  3. Page 194

  4. Avery’s Experiments (1940’s) • Avery’s work showed that DNA was the heredity material that transfers information between bacterial cells.

  5. Hershery-Chase Experiment • Hershey and Chase confirmed that DNA, and not protein, is the hereditary material. • Page 195

  6. Structure of DNA 10.2

  7. DNA – The Blueprint of Life • Established by James Watson and Francis Crick (1950’s) • DNA contains the instructions for making proteins within the cell. • Shape of a double helix • Made up of repeating sub-units called nucleotides

  8. DNA codes for genes • Gene - A segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color…etc.), a gene is a stretch of DNA.

  9. Deoxyribonucleic acid - DNA • Monomer: nucleotides • Each nucleotides has: • Deoxyribose sugar • Phosphate group • (1 of 4) nitrogen containing base

  10. The 4 Bases in DNA are: • Thymine (T) • Cytosine (C) • Guanine (G) • Adenine (A)

  11. Nitrogen Rings • Purines have double rings of carbon-nitrogen (G, A) • Pyrimidines have single carbon-nitrogen rings (C, T)

  12. Complementary Base Pairing • Base Pairing Rules 1. C and G 2. T and A

  13. Hydrogen Bonds • How do the nitrogenous bases stick together? • Hydrogen bonds • 3 H bonds hold G & C together • 2 H bonds hold T & A together

  14. DNA Replication 10.3 • Occurs when chromosomes duplicate before mitosis & meiosis • Makes an exact copy of the DNA • H bonds between bases break and enzymes “unzip” the molecule

  15. Steps of DNA Replication (pg. 201) • Enzymes called helicases separate the DNA strand breaking the H bonds at the replication fork • Enzymes called DNA polymerase add complementary nucleotides • DNA polymerase falls off when done replicating and the result is an identical strand of DNA

  16. Semi-conservative replication-Each old strand of nucleotides serves as a template for each new strand.

  17. Another View of Replication

  18. Protein Synthesis The Central Dogma: the flow of genetic information from DNA to RNA to Protein 10.4

  19. Protein Synthesis • 2 Parts • Transcription – makes a RNA molecule complementary to a portion of DNA. • Translation – occurs when the sequences of bases of mRNA directs the sequence of amino acids in a polypeptide.

  20. RNA • Ribonucleic Acid • 2nd type of nucleic acid • Monomer = nucleotide • Ribose sugar • 1 of 4 N bases • Phosphate group

  21. N-bases: • A, G, C, & U • Uracil replaces Thymine • Base pairing rules: A-U, G-C • Purpose:to transfer genetic material from DNA (inside the nucleus) to the site of protein synthesis (in the cytoplasm)

  22. How does RNA differ from DNA? • Different sugars (deoxyribose vs. ribose) • Different N-bases (thymine vs. uracil) • Different shapes (double helix vs. single strand)

  23. Types of RNA: • Messenger RNA (mRNA): • Carries genetic info from the nucleus to the cytoplasm • Transfer RNA (tRNA): • Carries specific amino acids to the ribosome to build the protein • Ribosomal RNA (rRNA): • Major component of the ribosome organelle • Site of protein synthesis • Most abundant type of RNA

  24. 3 Types of RNA

  25. How is RNA made? • Transcription • The process by which RNA is copied from DNA in the nucleus

  26. Steps of Transcription: • RNA polymerase binds to the promoter section of DNA • DNA unwinds and separates • RNA polymerase adds nucleotides complimentary to the DNA template strand • Process ends once RNA polymerase reaches the termination signal on the DNA

  27. Definitions: • RNA polymerase: enzyme use to make an RNA polymer from DNA • Promoter: Starting point on DNA • DNA template: Strand of DNA that RNA is complementary to (create from) • Termination signal: Ending point on DNA

  28. Products of Transcription: • mRNA, tRNA, & rRNA • All products move out of the nucleus and go into the cytoplasm to be used in protein synthesis DNA  RNA mRNA tRNA rRNA

  29. Protein Synthesis: • The making of proteins at the ribosome • The amount and kind of proteins produced in a cell determine its structure & function • Proteins carry out the genetic instruction in DNA

  30. Protein Review: • Monomer = amino acids • 20 different types • Linked together bypeptide bonds • Sequence of amino acids determines the proteins structure and function

  31. The Genetic Code: • The correlation between nucleotide sequence (DNA or RNA) and amino acid sequence (protein) • Codons: combination of 3 mRNA nucleotides that code for a specific amino acid

  32. Types of codons: • 64 codons code for 20 amino acids • Thus more than one codon codes for an AA • Start codon: (AUG) starts the process of translation • Stop codons: (UAA, UAG, UGA) ends the process of translation

  33. Circular Genetic Code

  34. Translation: • The process of assembling polypeptides (proteins) from nucleotide sequence in mRNA • “Translating” from one language (nucleotides) into another language (amino acids)

  35. Steps of Translation • During translation, amino acids are assembled from information encoded in mRNA • As mRNA codons move through the ribosome, tRNA’s add specific amino acids to the growing polypeptide chain. • The process continues until a stop codon is reached and the newly made protein is released.

  36. So what is the Central Dogma? • The flow from DNA to RNA to Protein

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