Protein synthesis


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Protein synthesis

  1. 1. Gene Activity: How Genes Work Mader: Biology 8 th Ed.
  2. 2. Outline <ul><li>Function of Genes </li></ul><ul><ul><li>One Gene-One Enzyme Hypothesis </li></ul></ul><ul><li>Genetic Code </li></ul><ul><li>Transcription </li></ul><ul><ul><li>Processing Messenger RNA </li></ul></ul><ul><li>Translation </li></ul><ul><ul><li>Transfer RNA </li></ul></ul><ul><ul><li>Ribosomal RNA </li></ul></ul>Mader: Biology 8 th Ed.
  3. 3. Function of Genes <ul><li>Genes Specify a Polypeptide </li></ul><ul><ul><li>The one gene-one enzyme hypothesis suggests a genetic mutation causes a change in the structure of a protein. </li></ul></ul><ul><ul><ul><li>A gene is a segment of DNA that specifies the sequence of amino acids in a polypeptide of a protein. </li></ul></ul></ul>Mader: Biology 8 th Ed.
  4. 4. From DNA to RNA to Protein <ul><li>Central Dogma of Molecular Biology: </li></ul><ul><ul><li>Genes code for the sequence of nucleotides in RNA molecules. </li></ul></ul><ul><ul><ul><li>RNA brings about formation of a protein coded for by DNA of a particular gene. </li></ul></ul></ul>Mader: Biology 8 th Ed. Transcription DNA Replication mRNA Translation PROTEIN Nucleus Cytoplasm
  5. 5. DNA Replication Mader: Biology 8 th Ed.
  6. 6. RNA <ul><li>Uracil (U) replaces thymine (T) of DNA. </li></ul><ul><ul><li>Types of RNA </li></ul></ul><ul><ul><ul><li>Messenger (mRNA) - Takes message from DNA in nucleus to ribosomes in cytoplasm. </li></ul></ul></ul><ul><ul><ul><li>Transfer (tRNA) - Transfers amino acids to ribosomes. </li></ul></ul></ul><ul><ul><ul><li>Ribosomal (rRNA) - Help make up ribosomes. </li></ul></ul></ul>Mader: Biology 8 th Ed.
  7. 7. Structure of RNA Mader: Biology 8 th Ed.
  8. 8. Mader: Biology 8 th Ed.
  9. 9. Steps of Gene Expression <ul><li>During transcription , DNA serves as a template for RNA formation. </li></ul><ul><li>During translation , an mRNA transcript directs the sequence of amino acids in a polypeptide. </li></ul>Mader: Biology 8 th Ed.
  10. 10. Gene Expression Mader: Biology 8 th Ed.
  11. 11. The Genetic Code <ul><li>There is a genetic code for each of the 20 amino acids found in proteins. </li></ul><ul><ul><li>Genetic code is a triplet code , with each codon consisting of three nucleotide bases. </li></ul></ul><ul><ul><ul><li>Code Properties </li></ul></ul></ul><ul><ul><ul><ul><li>Universal </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Degenerate </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Unambiguous </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Contains start and stop signals </li></ul></ul></ul></ul>Mader: Biology 8 th Ed.
  12. 12. Mader: Biology 8 th Ed.
  13. 13. Transcription <ul><li>During transcription, an mRNA molecule is formed with a sequence of bases complementary to a portion of one DNA strand. </li></ul><ul><ul><li>RNA polymerase joins the nucleotides together in 5’  3’ direction. </li></ul></ul><ul><ul><ul><li>Promoter defines start of a gene, the direction of transcription, and the strand to be transcribed. </li></ul></ul></ul><ul><ul><ul><ul><li>Elongation continues until polymerase comes to a DNA terminator sequence. </li></ul></ul></ul></ul>Mader: Biology 8 th Ed.
  14. 14. Transcription Mader: Biology 8 th Ed.
  15. 15. Processing Messenger RNA <ul><li>Newly formed mRNA molecule, primary mRNA transcript, is modified before it leaves the eukaryotic nucleus. </li></ul><ul><ul><li>Cap on 5’ end, and poly-A tail on 3’ end. </li></ul></ul><ul><ul><li>Introns are removed during RNA processing, leaving only exons . </li></ul></ul><ul><ul><ul><li>Mature mRNA </li></ul></ul></ul><ul><ul><ul><ul><li>In most cases, mRNA splicing is done by a spliceosome. </li></ul></ul></ul></ul>Mader: Biology 8 th Ed.
  16. 16. Mader: Biology 8 th Ed.
  17. 17. Translation <ul><li>Transfer RNA molecules transfer amino acids to the ribosomes. </li></ul><ul><ul><li>tRNA molecules bind with one particular amino acid, and bear an anticodon complementary to the codon for that amino acid. </li></ul></ul><ul><ul><ul><li>tRNA synthetases attach correct amino acid to the correct tRNA molecule. </li></ul></ul></ul>Mader: Biology 8 th Ed.
  18. 18. Transfer RNA Mader: Biology 8 th Ed.
  19. 19. Role of Ribosomal RNA <ul><li>Ribosomal RNA (rRNA) is produced off a DNA template in the nucleolus of a nucleus. </li></ul><ul><ul><li>Packaged with proteins into ribosomal subunits, one larger than the other. </li></ul></ul><ul><ul><ul><li>Contain binding sites to facilitate complementary base pairing between tRNA anticodons and mRNA codons. </li></ul></ul></ul>Mader: Biology 8 th Ed.
  20. 20. <ul><li>Ribosomes consist of two subunits. </li></ul><ul><ul><li>The large subunit has three binding sites for tRNA. </li></ul></ul><ul><ul><li>The small subunit binds to mRNA. </li></ul></ul>
  21. 21. Ribosome Structure and Function Mader: Biology 8 th Ed.
  22. 22. Mader: Biology 8 th Ed.
  23. 23. A. Initiation Mader: Biology 8 th Ed.
  24. 24. B. Elongation Mader: Biology 8 th Ed.
  25. 25. Mader: Biology 8 th Ed.
  26. 26. C. Termination Mader: Biology 8 th Ed.
  27. 27. Online Activities and Tutorials Mader: Biology 8 th Ed.