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04PO, p. 896. 28CO, p. 898. Fig. 28-2, p. 899. Fig. 28-3, p. 900. Fig. 28-3a, p. 900. Fig. 28-3b, p. 900. Fig. 28-3c, p. 900. Fig. 28-4, p. 901. Fig. 28-5, p. 902. Fig. 28-5a, p. 902. Fig. 28-5b, p. 902. Fig. 28-6, p. 903. Fig. 28-6a, p. 903. Fig. 28-6b, p. 903. Table 28-1, p. 904. - PowerPoint PPT Presentation

Transcript of 04PO, p. 896

  • 04PO, p. 896

  • 28CO, p. 898

  • Fig. 28-2, p. 899

  • Fig. 28-3, p. 900

  • Fig. 28-3a, p. 900

  • Fig. 28-3b, p. 900

  • Fig. 28-3c, p. 900

  • Fig. 28-4, p. 901

  • Fig. 28-5, p. 902

  • Fig. 28-5a, p. 902

  • Fig. 28-5b, p. 902

  • Fig. 28-6, p. 903

  • Fig. 28-6a, p. 903

  • Fig. 28-6b, p. 903

  • Table 28-1, p. 904

  • Fig. 28-7, p. 905

  • Fig. 28-8, p. 906

  • Table 28-2, p. 906

  • Fig. 28-9a, p. 907

  • Fig. 28-9b, p. 907

  • Fig. 28-10, p. 907

  • Table 28-3, p. 908

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  • Fig. 28-11, p. 909

  • Fig. 28-12, p. 910

  • Fig. 28-13, p. 911

  • Fig. 28-14a, p. 912

  • Fig. 28-14b, p. 912

  • Table 28-4, p. 912

  • Fig. 28-15, p. 913

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  • Fig. 28-15b, p. 913

  • Fig. 28-16, p. 915

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  • Fig. 28-17, p. 917

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  • Fig. 28-17c, p. 917

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  • Fig. 28-23a, p. 922

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  • Fig. 28-24, p. 925

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  • Fig. 28-24c, p. 925

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  • Fig. 28-25, p. 928

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  • Fig. 28-26c, p. 929

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  • Fig. 28-26e, p. 929

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  • Fig. 28-27, p. 930

  • Fig. 28-27a, p. 930

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  • Fig. 28-27c, p. 930

  • Fig. 28-28, p. 931

  • Fig. 28-29, p. 931

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  • Fig. 28-30, p. 931

  • Fig. 28-30a, p. 931

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  • Fig. 28-31, p. 932

  • Fig. 28-31a, p. 932

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  • Fig. 28-31c, p. 932

  • Fig. 28-31d, p. 932

  • Fig. 28-31e, p. 932

  • Fig. 28-32, p. 934

  • Fig. 28-33, p. 935

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  • Fig. 28-33b, p. 935

  • Fig. 28-33c, p. 935

  • Fig. 28-34, p. 936

  • Fig. 28-34a, p. 936

  • Fig. 28-34b, p. 936

  • Fig. 28-35, p. 937

  • Fig. 28-36, p. 938

  • Fig. 28-36a, p. 938

  • Fig. 28-36b, p. 938

  • Fig. 28-36c, p. 938

  • Fig. 28-36d, p. 938

  • Fig. 28-37, p. 938

    Julie Newdolls painting Dawn of the Double Helix composes the DNA duplex as human figures. Her theme in this painting is Life Forms: The basic structures that make our existence possible. Thomas Hardys poem captures the immortality of DNA as the eternal thing in man, That heeds no call to die, or as Richard Dawkins wryly comments, the individual is just DNAs way of making more DNA! FIGURE 28.2 Untwisting of DNA strands exposes their bases for hydrogen bonding. Base pairing ensures that appropriate nucleotides are inserted in the correct positions as the new complementary strands are synthesized. By this mechanism, the nucleotide sequence of one strand dictates a complementary sequence in its daughter strand. The original strands untwist by rotating about the axis of the unreplicated DNA double helix. ANIMATED FIGURE 28.3 Three models of DNA replication prompted by Watson and Cricks double helix structure for DNA. (a) Conservative: Each strand of the DNA duplex is replicated, and the two newly synthesized strands join to form one DNA double helix while the two parental strands remain associated with each other. The products are one completely new DNA duplex and the original DNA duplex. (b) Semiconservative: The two strands separate, and each strand is copied to generate a complementary strand. Each parental strand remains associated with its newly synthesized complement, so each DNA duplex contains one parental strand and one new strand. (c) Dispersive: This model predicts that each of the four strands in the two daughter DNA duplexes contains both newly synthesized segments and segments derived from the parental strands. See this figure animated at http:// chemistry.brookscole.com/ggb3 (a) Conservative: Each strand of the DNA duplex is replicated, and the two newly synthesized strands join to form one DNA double helix while the two parental strands remain associated with each other. The products are one completely new DNA duplex and the original DNA duplex.(b) Semiconservative: The two strands separate, and each strand is copied to generate a complementary strand. Each parental strand remains associated with its newly synthesized complement, so each DNA duplex contains one parental strand and one new strand.(c) Dispersive: This model predicts that each of the four strands in the two daughter DNA duplexes contains both newly synthesized segments and segments derived from the parental strands.FIGURE 28.4 The Meselson and Stahl experiment demonstrating that DNA replication is semiconservative. On the left are densitometric traces made of UV absorption photographs taken of the ultracentrifugation cells containing DNA isolated from E. coli grown for various generation times after 15N-labeling. The photographs were taken once the migration of the DNA in the density gradient had reached equilibrium. Density increases from left to right. The peaks reveal the positions of the banded DNA with respect to the density of the solution. The number of generations that the E. coli cells were grown (following 14 generations of 15N density-labeling) is shown down the middle. A schematic representation interpreting the pattern expected of semiconservative replication is shown on the right side of this figure. (Adapted from Meselson, M., and Stahl, F. W., 1958. The replication of DNA. Proceedings of the National Academy of Sciences, U.S.A. 44:671682.) FIGURE 28.5 Bidirectional replication of the E. coli chromosome. (a) If replication is bidirectional, autoradiograms of radioactively labeled replicating chromosomes should show two replication forks heavily labeled with radioactive thymidine. (b) An autoradiogram of the chromosome from a dividing E. coli cell shows bidirectional replication. (Photo courtesy of David M. Prescott, University of Colorado.)(a) If replication is bidirectional, autoradiograms of radioactively labeled replicating chromosomes should show two replication forks heavily labeled with radioactive thymidine.(b) An autoradiogram of the chromosome from a dividing E. coli cell shows bidirectional replication.ANIMATED FIGURE 28.6 The semidiscontinuous model for DNA replication. Newly synthesized DNA is shown as red. Because DNA polymerases only polymerize nucleotides 53, both strands must be synthesized in the 53 direction. Thus, the copy of the parental 35 strand is synthesized continuously; this newly made strand is designated the leading strand. (a) As the helix unwinds, the other parental strand (the 53 strand) is copied in a discontinuous fashion through synthesis of a series of fragments 1000 to 2000 nucleotides in length, called the Okazaki fragments; the strand constructed from the Okazaki fragments is called the lagging strand. (b) Because both strands are synthesized in concert by a dimeric DNA polymerase situated at the replication fork, the 53 parental strand must wrap around in trombone fashion so that the unit of the dimeric DNA polymerase replicating it can move along it in the 35 direction. This parental strand is copied in a discontinuous fashion because the DNA polymerase must occasionally dissociate from this strand and rejoin it further along. The Okazaki fragments are then covalently joined by DNA ligase to form an uninterrupted DNA strand. See this figure animated at http://chemistry.brookscole.com/ggb3 (a) As the helix unwinds, the other parental strand (the 53 strand) is copied in a discontinuous fashion through synthesis of a series of fragments 1000 to 2000 nucleotides in length, called the Okazaki fragments; the strand constructed from the Okazaki fragments is called the lagging strand.(b) Because both strands are synthesized in concert by a dimeric DNA polymerase situated at the replication fork, the 53 parental strand must wrap around in trombone fashion so that the unit of the dimeric DNA polymerase replicating it can move along it in the 35 direction. This parental strand is copied in a discontinuous fashion because the DNA polymerase must occasionally dissociate from this strand and rejoin it further along. The Okazaki fragments are then covalently joined by DNA ligase to form an uninterrupted DNA strand.FIGURE 28.7 The chain elongation reaction catalyzed by DNA polymerase. DNA polymerase I joins deoxynucleoside monophosphate units to the 3-OH end of the primer, employing dNTPs as substrates. The 3-O