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DNA Structure and Function

DNA Structure and Function. Chapter 5 part 1. monomer. adenine (A). deoxyadenosine triphosphate, a purine. Fig. 13-4a, p. 206. guanine (G). deoxyguanosine triphosphate, a purine. Fig. 13-4b, p. 206. thymine (T). deoxythymidine triphosphate, a pyrimidine. Fig. 13-4c, p. 206.

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DNA Structure and Function

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  1. DNA Structure and Function Chapter 5 part 1

  2. monomer

  3. adenine (A) deoxyadenosine triphosphate, a purine Fig. 13-4a, p. 206

  4. guanine (G) deoxyguanosine triphosphate, a purine Fig. 13-4b, p. 206

  5. thymine (T) deoxythymidine triphosphate, a pyrimidine Fig. 13-4c, p. 206

  6. cytosine (C) deoxycytidine triphosphate, a pyrimidine Fig. 13-4d, p. 206

  7. Structure of DNA

  8. Rosalind Franklin’s X-Ray Diffraction Image

  9. Patterns of Base Pairing • The sequence of bases is the genetic code • Variation in base sequences gives life diversity

  10. Fig. 13-5b, p. 207

  11. DNA Replication dispersive

  12. The parent DNA double helix unwinds in this direction. Only one new DNA strand is assembled continuously. The other new DNA strand is assembled in many pieces. 3’ 5’ Gaps are sealed by DNA ligase. 3’ 5’ 5’ 3’ Fig. 13-8b, p. 209

  13. A A DNA molecule is double-stranded. The two strands of DNA stay zippered up together because they are complementary: their nucleotides match up according to base-pairing rules (G to C, T to A). B As replication starts, the two strands of DNA are unwound. In cells, the unwinding occurs simul- taneously at many sites along the length of each double helix. C Each of the two parent strands serves as a template for assembly of a new DNA strand from free nucleotides, according to base-pairing rules (G to C, T to A). Thus, the two new DNA strands are complementary in sequence to the parental strands. D DNA ligase seals any gaps that remain between bases of the “new” DNA, so a continuous strand forms. The base sequence of each half-old, half-new DNA molecule is identical to that of the parent DNA molecule. Stepped Art Fig. 13-6, p. 208

  14. Enzymes of DNA Replication • DNA helicase • Breaks hydrogen bonds between DNA strands • DNA polymerase • Joins free nucleotides into a new strand of DNA

  15. Checking for Mistakes • DNA repair mechanisms • DNA polymerases proofread DNA sequences during DNA replication and repair damaged DNA • When proofreading and repair mechanisms fail, an error becomes a mutation– a permanent change in the DNA sequence

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