05 dna

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05 dna

  1. 1. DNA • THE CHEMISTRY OF HEREDITY (11.1) • DNA REPLICATION (11.1)
  2. 2. Answer these questions: • WHERE DO ALL CELLS COME FROM (CELL THEORY)? • WHAT IS HEREDITY?
  3. 3. The Chemistry of Heredity  Heredity  The passing of traits to offspring from parents  Traits  Physical and chemical characteristics  The result of protein synthesis  Answer this question:  What controls protein synthesis?
  4. 4. The Chemistry of Heredity  DNA controls protein synthesis  Genes make up DNA  Genes control the formation of protein  Genetics  The study of genes  Why characteristics appear  The processes of heredity
  5. 5. The Chemistry of Heredity  Answer these questions:  What makes two proteins different? (Hint: think primary structure)  Where are proteins assembled?  Proteins differ by amino acid arrangement  The order of amino acids  Proteins are assembled at the ribosome  Genes tell the sequence of amino acids  The sequence is read at the ribosome  The ribosome joins the amino acids in the proper order
  6. 6. The Chemistry of Heredity  The Discovery of DNA  Answer these questions:  What is the monomer of DNA?  What are the 4 monomers found in DNA?
  7. 7. The Chemistry of Heredity  Deoxyribonucleic acid (DNA) – The Double Helix  DNA is a polymer  The monomer units of DNA are nucleotides  Each nucleotide is made of a: 5-carbon sugar (deoxyribose)  Nitrogen containing base  Phosphate group 
  8. 8. The Chemistry of Heredity  There are 4 types of nucleotides, differing only in the nitrogenous base  Adenine (A)  Guanine (G)  Cytosine (C)  Thymine (T)  A and G are called purines  C and T are called pyrimidines
  9. 9. Purines  Adenine (A) and Guanine (G) are composed of two rings
  10. 10. Pyrimidines  Cytosine (C) and Thymine (T) are composed of one ring
  11. 11. The Chemistry of Heredity  The nitrogen containing base (purines and pyrimidines) attaches to deoxyribose (5-carbon sugar) to form a ‘nucleoside’
  12. 12. Deoxyribose  To keep track of where things attach, we number the carbons
  13. 13. Nucleoside Answer this question: Which carbon is the nitrogen base attached to?
  14. 14. The Chemistry of Heredity  A nucleotide is a nucleoside with an attached phosphate group (attached where?)
  15. 15. The Chemistry of Heredity  Phosphate groups join the deoxyribose sugars together in a chain-like fashion
  16. 16. The Chemistry of Heredity  DNA is made of 2 complimentary chains of nucleotides where…  A forms 2 hydrogen bonds with T  G forms 3 hydrogen bonds with C  The bases (A, T, G, C) are hydrophobic  Where will they go?
  17. 17. The Chemistry of Heredity  The series of nucleotide units makes one organisms’ DNA different from another  Different DNA = Different Traits  Every cell of a multicellular organism has the same DNA (remember, we all start as one cell)
  18. 18. Answer these questions: •W H A T K I N D O F B O N D S H O L D T H E T W O S T R A N D S I N D N A TOGETHER? • WHAT ARE THE 4 BASES AND HOW ARE THEY CATEGORIZED? • WHAT DOES AN ENZYME DO?
  19. 19. DNA Replication  DNA replication is the process whereby an entire double-stranded DNA is copied to produce a second, identical DNA double helix
  20. 20. DNA Replication  The Replication Factory  DNA replication is carried out by proteins  These special proteins cluster together ( replication factory)  DNA is fed through the replication factory  The incoming DNA double helix is split into two single strands and each original single strand becomes half of a new DNA double helix   This is a semi-conservative process http://www.wiley.com/college/pratt/0471393878/student/ani mations/dna_replication/index.html
  21. 21. DNA Replication  DNA Replication Proteins  Helicase   Single-stranded binding proteins (SSBs)   Unwinds the DNA double helix into 2 individual strands Coats the single-stranded DNA, preventing the two strands from realigning Primase  Gets each strand ready (or primed) for replication by adding a small amount of RNA to each strand to show DNA polymerase where to start
  22. 22. DNA Replication  DNA Replication Proteins  DNA Polymerase   RNAse H   Strings nucleotides together to form a new DNA strand Removes the RNA primers (set by primase) DNA ligase  Links short stretches of DNA together to create one long continuous DNA strand
  23. 23. DNA Replication  Step 1: Strand Separation  The two strands that make up the double helix are unwound and separated by the enzyme helicase  Single-stranded binding proteins (SSBs) quickly coat the newly exposed single strands  Without the SSBs, the complementary DNA strands could easily snap back together
  24. 24. DNA Replication  Step 2: New Strand Synthesis  The two single strands of DNA act as templates for the production of two new, complimentary DNA strands  The two strands that makes up a double helix are antiparallel   Complementary 5’ to 3’ strands running in opposite directions Strand synthesis proceeds in a 5’ to 3’ direction
  25. 25. New Strand Synthesis 1. Primase copies a short stretch of the DNA strand, creating a complementary RNA segment, showing DNA polymerase where to start
  26. 26. New Strand Synthesis 2. DNA polymerase can now begin synthesizing a new complimentary DNA strand Two DNA polymerase enzymes are required, one for each strand Since the strands are antiparallel, the DNA polymerase enzymes begin to move in opposite directions One DNA polymerase copies continuously in one direction. This strand is called the leading strand The other must synthesize in small fragments. This strand is called the lagging strand 1. 2. 3. 4. 1. The small fragments are called Okazaki fragments
  27. 27. New Strand Synthesis 3. RNAse H removes the primers (set by primase) The gaps left by the primers are filled by DNA polymerase 5. Finally, the Okazaki fragments are joined by DNA ligase 4. http://www.wiley.com/college/pratt/0471393878/student/animations/d na_replication/index.html http://www.youtube.com/watch?v=5VefaI0LrgE

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