© 2011 Pearson Education, Inc. 1 Chapter 28 The Chemistry of the Nucleic Acids Organic Chemistry 6 th Edition Paula Yurkanis Bruice

© 2011 Pearson Education, Inc. 2 Nucleic Acids

© 2011 Pearson Education, Inc. 3 In nucleic acids, the phosphate group is a phosphodiester:

© 2011 Pearson Education, Inc. 4 The Bases in Nucleic Acids Adenine, guanine, cytosine, and thymine are found in DNA. Adenine, guanine, cytosine, and uracil are found in RNA.

© 2011 Pearson Education, Inc. 5 Nucleosides = Base + Sugar

© 2011 Pearson Education, Inc. 6 Nucleotides = Base + Sugar + Phosphate

© 2011 Pearson Education, Inc. 7

8 Different Forms of Nucleotides

© 2011 Pearson Education, Inc. 9 Other Important Nucleotides Cyclic AMP and cyclic GMP serve as a link between several hormones and certain enzymes that regulate cellular function

© 2011 Pearson Education, Inc. 10 Nitric Oxide Transduction Pathway The cGMP second messenger causes blood vessel dilation

© 2011 Pearson Education, Inc. 11 Cyclic Nucleotide Messengers Are Terminated by Phosphodiesterases Viagra is a phosphodiesterase inhibitor that extends the cGMP message

© 2011 Pearson Education, Inc. 12 Nucleic Acids Are Composed of Nucleotide Subunits

© 2011 Pearson Education, Inc. 13 DNA Is Synthesized in the 5 to 3 Direction

© 2011 Pearson Education, Inc. 14 Complementary Base Pairing in DNA

© 2011 Pearson Education, Inc. 15 Base Pairing in DNA

© 2011 Pearson Education, Inc. 16 The sugar–phosphate backbone is on the outside, and the bases are on the inside:

© 2011 Pearson Education, Inc. 17 The DNA Double Helix

© 2011 Pearson Education, Inc. 18 DNA Is More Stable Than RNA

© 2011 Pearson Education, Inc. 19 Replication of DNA

© 2011 Pearson Education, Inc. 20 Transcription: synthesis of RNA from a DNA blueprint Promoter: marks the beginning of a gene Sense strand: informational strand Anti-sense or template: used to synthesize RNA

© 2011 Pearson Education, Inc. 21 Transcription of DNA A stretch of bases representing a portion of a gene is called an exon. A stretch of bases that contains no genetic information is called an intron. mRNA is spliced prior to leaving the nucleus.

© 2011 Pearson Education, Inc. 22 Translation: synthesis of a protein from an RNA blueprint There are three kinds of RNA: Messenger RNA (mRNA) determines the sequences of amino acids in a protein. Ribosomal RNA (rRNA) is a component of ribosomes, where protein synthesis takes place. Transfer RNA (tRNA) is the carrier of amino acids for protein synthesis.

© 2011 Pearson Education, Inc. 23 A Transfer RNA

© 2011 Pearson Education, Inc. 24 The Proposed Mechanism for Aminoacyl-tRNA Synthetase

© 2011 Pearson Education, Inc. 25 The Substrate-Binding Site for tRNA His

© 2011 Pearson Education, Inc. 26 A protein is synthesized from its N-terminal end to its C- terminal end. Each amino acid is specified by a three-base sequence known as the genetic code.

© 2011 Pearson Education, Inc. 27 Translation

© 2011 Pearson Education, Inc. 28

© 2011 Pearson Education, Inc. 29 L-Hydroxyproline CCU CCC CCA CCG Proline codes Sold in health food stores to support connective tissue. Does it work? No. L-Hydroxyproline is not incorporated into connective tissue, because it has no genetic code L-Hydroxyproline L-Hydroxyproline, the major amino acid in collagen, results from the post-translational oxidation of proline

© 2011 Pearson Education, Inc. 30 Why does DNA contain thymine instead of uracil although the synthesis of thymine is energetically expensive? Because thymine prevents potentially lethal mutations

© 2011 Pearson Education, Inc. 31 Because cytosine can be converted to uracil… Having T’s in place of U’s in DNA allows the U’s that are found in DNA to be recognized as mistakes How does the presence of thymine prevent mutations?

© 2011 Pearson Education, Inc. 32 Large DNA can be cleaved into smaller fragments by restriction endonucleases:

© 2011 Pearson Education, Inc. 33 DNA Sequencing

© 2011 Pearson Education, Inc. 34

© 2011 Pearson Education, Inc. 35 Polymerase Chain Reaction (PCR) strand separation base pairing with primers DNA synthesis

© 2011 Pearson Education, Inc. 36 Laboratory Synthesis of DNA

© 2011 Pearson Education, Inc. 37

© 2011 Pearson Education, Inc. 38 Oligonucleotide Synthesis with Phosphoramidites

© 2011 Pearson Education, Inc. 39 The amino groups of the bases must be protected:

© 2011 Pearson Education, Inc. 40 Removal of the Protecting Group by Ammonia

© 2011 Pearson Education, Inc. 41 Utilization of H-phosphate monomer to synthesize DNA strand

© 2011 Pearson Education, Inc. 42