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3.a&p i dna.2010


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3.a&p i dna.2010

  2. 2. Readings for DNA and Protein Synthesis <ul><li>Chap. 3: pages 93; 96; 100-107 </li></ul><ul><li>Skim text - concentrate on lecture notes </li></ul>
  3. 3. <ul><li>Importance and structure of DNA: Deoxyribose Nucleic Acid </li></ul><ul><li>A. Historical Review </li></ul><ul><ul><li>1. 1900s - Morgan’s studies with fruit flies showed that genes were located on chromosomes, and chromosomes consisted of protein and DNA </li></ul></ul><ul><ul><li>2. 1952 - Hershey-Chase demonstrated that DNA (not protein) was the genetic material of a viral phage </li></ul></ul>
  4. 4. B. Structure of DNA <ul><li>1. Nucleotide monomers: </li></ul><ul><ul><li>Phosphate </li></ul></ul><ul><ul><li>Pentose sugar(C 5 ) (Deoxyribose sugar) </li></ul></ul><ul><ul><li>Organic Nitrogen group: cytosine, adenine, guanine, thymine </li></ul></ul>
  5. 5. B. Structure of DNA (continued) <ul><li>2. Polynucleotide chain with linkage via phosphates to next sugar, with nitrogen base away from backbone of Phos-Sugar-Phos-Sugar </li></ul><ul><li>3. Dehydration synthesis </li></ul>
  6. 7. <ul><li>4. 1954 - classical one page paper in Nature by Watson & Crick using Franklin’s and Wilkins’ data </li></ul><ul><li>A double helix - 2 polynucleotide strands </li></ul><ul><li>Sugar-phosphate chains of each strand are like the side ropes of a rope ladder </li></ul><ul><li>Pairs of nitrogen bases, one from each strand, form the rungs or steps </li></ul><ul><li>The ladder forms a twist every 10 bases (all from x-ray studies!) </li></ul>
  7. 9. <ul><li>5. Later confirmation that: </li></ul><ul><li># of adenine equal to # of thymine </li></ul><ul><li># of guanine equal to # of cytosine </li></ul><ul><li>This dictates combinations of N-bases that form steps/rungs </li></ul><ul><li>Does not restrict the sequence of bases along each DNA strand </li></ul>
  8. 10. Fig. 3.32
  9. 11. C. Replication / Duplication of DNA <ul><li>1. Due to complimentary base pairing – one strand of DNA polynucleotide determines the sequence of the other polynucleotide strand </li></ul><ul><li>2. Therefore, each strand of double stranded DNA acts as a template </li></ul><ul><li>3. The double helix first unwinds – controlled by enzymes and uses new nucleotides that are free in the nucleus to copy a complimentary strand off the original DNA strand </li></ul>
  10. 12. Models of DNA Replication <ul><li>View A&P Animation - Structure & Replication </li></ul><ul><li>View 16-07 L4 from BIO text </li></ul><ul><li>View animation 16-10 (3 and 2) </li></ul><ul><li>View 16-11 </li></ul>
  11. 13. 4. Information storage in DNA <ul><li>The 4 nitrogen bases are the “alphabet” or code for all the traits an organism possesses </li></ul><ul><li>Different genes or traits vary in the sequence and length of the bases </li></ul><ul><li>ATTTCGGAC vs..... ATTTAC </li></ul><ul><li>Every three bases = one amino acid in a protein/peptide </li></ul>
  12. 14. II. Ribonucleic Acid (RNA) <ul><li>A. Structure of RNA </li></ul><ul><ul><li>1. Nucleotide monomer </li></ul></ul><ul><ul><ul><li>Phosphate </li></ul></ul></ul><ul><ul><ul><li>Pentose sugar = ribose (extra oxygen) </li></ul></ul></ul><ul><ul><ul><li>Nitrogen base = A / G / C plus U = uracil instead of thymine </li></ul></ul></ul><ul><ul><ul><li>Single stranded - possibly </li></ul></ul></ul><ul><ul><ul><li>3 types (messenger/transfer/ribosomal RNA) </li></ul></ul></ul>
  13. 15. B. Synthesis of RNA - Transcription <ul><li>1. DNA acts as template, but only one strand of DNA utilized at a given time </li></ul><ul><li>2. This exposed strand is controlled by specific enzymes that pair the DNA nucleotides with free RNA nucleotides, which are also present in the nucleus </li></ul><ul><li>3. These RNA nucleotides form a single stranded RNA nucleic acid </li></ul><ul><li>4. DNA = ATTCGCAT </li></ul><ul><li>5. RNA = UAAGCGUA </li></ul><ul><li>6. Short segments of DNA transcribed at a time, with start and stop messages </li></ul>
  14. 17. <ul><li>View 17-02 </li></ul><ul><li>View 17-06 movie </li></ul><ul><li>View 17-06 photos </li></ul>
  15. 18. C. Three types of RNA <ul><li>1. m-RNA: messenger RNA </li></ul><ul><ul><li>Transcribed from a specific segment of DNA which represents a specific gene or genetic unit </li></ul></ul><ul><li>2. t-RNA: transfer RNA </li></ul><ul><ul><li>Transcribed from different segments of DNA and their function is to find a specific amino acid in cytoplasm and bring it to the mRNA </li></ul></ul><ul><li>3. r-RNA: ribosomal RNA </li></ul><ul><ul><li>Transcribed at the nucleolus -with proteins function as the site of protein synthesis ( in cytoplasm) </li></ul></ul>
  16. 19. Three types of RNA
  17. 20. III. Protein synthesis = Translation <ul><li>A. Ribosomes = sites of protein synthsis </li></ul><ul><ul><li>1. 30 to 40% protein </li></ul></ul><ul><ul><li>2. 60 to 70% RNA (rRNA) </li></ul></ul><ul><ul><li>3. Assembled in nucleus and exported via nuclear pores </li></ul></ul><ul><ul><li>4. Antibiotics can paralyze bacterial ribosomes, but not eukaryotic ribosomes </li></ul></ul><ul><ul><li>5. 2 ribosomal subunits - a large and a small </li></ul></ul><ul><ul><li>6. There are three sites on the ribosome that are involved in protein synthesis </li></ul></ul>
  18. 21. A. Ribosomes (continued) - bring mRNA together with amino acid bearing tRNAs <ul><li>8. Three ribosomal sites </li></ul><ul><ul><li>P site - (peptidyl-tRNA) holds the tRNA carrying the growing peptide chain, after several amino acids have been added </li></ul></ul><ul><ul><li>A site - (aminoaccyl-tRNA) holds the next single amino acid to be added to the chain </li></ul></ul><ul><ul><li>E site - (exit site) site where discharged tRNA minus amino acids leave ribosome </li></ul></ul>
  19. 23. C. Protein Synthesis <ul><li>1. One mRNA can bind to several ribosomes termed a polyribosome </li></ul><ul><li>17-17 movie and stills </li></ul><ul><li>17-18 </li></ul><ul><li>17-19 </li></ul><ul><li>17-20 </li></ul><ul><li>17-21 </li></ul>
  20. 24. Fig. 3.37 modified
  21. 26. Fig. 3.37
  22. 27. Fig. 3.38 modified