Unit B7 8 Protein Synthesis2


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Unit B7 8 Protein Synthesis2

  1. 1. Unit B7 - 8: Cell Biology (Protein Synthesis) Authored by Michelle Choma © <ul><li>Students who have fully met the prescribed learning outcomes (PLO’s) are able to: </li></ul><ul><li>B7. Demonstrate an understanding of the process of protein synthesis. </li></ul><ul><ul><li>identify the roles of DNA, mRNA, tRNA, and ribosomes in the process of transcription and translation, including initiation, elongation, and termination. </li></ul></ul>
  2. 2. Unit B7 Continued <ul><ul><li>determine the sequence of amino acids coded for by a specific DNA sequence (genetic code), given a table of mRNA codons. </li></ul></ul><ul><ul><li>identify the complementary nature of the mRNA codon and the tRNA anti-codon. </li></ul></ul>
  3. 3. B8. Explain how mutations in DNA affect protein synthesis. <ul><ul><li>give examples of two environmental mutagens that can cause mutations in humans. </li></ul></ul><ul><ul><li>use examples to explain how mutations in DNA change the sequence of amino acids in a polypeptide chain, and as a result may lead to genetic disorders. </li></ul></ul>
  4. 4. Web Sites & Links for Protein Synthesis <ul><li>http://www.coolschool.ca/lor/BI12/unit6/U06L00.htm (Unit 06) </li></ul><ul><ul><li>☺ Scroll to Lesson 01 – Lesson 04 (‘U06L01 – L04’) </li></ul></ul><ul><li>http://highered.mcgraw-hill.com/sites/0072421975/student_view0/chapter24/ </li></ul><ul><ul><li>(Mader’s Student Edition Website Support for Chapter 24; Animations, quizzes, flashcards, Thinking Scientifically etc.) </li></ul></ul><ul><ul><li>http://sps.k12.ar.us/massengale/pwpt_biology.htm </li></ul></ul><ul><ul><li>Power point presentation on Protein Synthesis </li></ul></ul><ul><li>http://sps.k12.ar.us/massengale/nucleic_acids_.htm </li></ul><ul><ul><li>(Nucleic acids & protein synthesis, animations) </li></ul></ul>
  5. 5. Some more…. <ul><li>http:// www.phschool.com/science/biology_place/index.html </li></ul><ul><ul><li>Check out the ‘ The Biology Place ’; Click on link to ‘BioCoach’ activities on Transcription & Translation. </li></ul></ul><ul><ul><li>Fabulous Reviews, Animations, Practice & Self-quiz etc. </li></ul></ul><ul><li>http://www.scilinks.org/retrieve.asp </li></ul><ul><ul><li>(Sign up on this site. Great links on protein synthesis: Link code, cbn-4123) </li></ul></ul><ul><li>http://www.phschool.com/webcodes10/index.cfm?wcprefix=cbe&wcsuffix=4123&fuseaction=home.gotoWebCode&x=11&y=18 </li></ul><ul><ul><li>(Great animation on protein synthesis) </li></ul></ul>
  6. 6. And some more…. <ul><li>http:// www.pbs.org/wgbh/aso/tryit/dna/shockwave.html </li></ul><ul><li>http://www.pbs.org/wgbh/aso/tryit/dna/index.html# </li></ul><ul><li>(Protein Synthesis activity & animation) </li></ul><ul><li>http://nobelprize.org/educational_games/medicine/dna/intro.html (Review & Animations of protein synthesis) </li></ul><ul><li>http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302 </li></ul><ul><li>http://www.eurekacityschools.org/ehs/riggsw/Transcription.ppt (Powerpoint) </li></ul><ul><li>http://learn.genetics.utah.edu/ (Animation) </li></ul><ul><li>Terrific activities. Check out the Genetics Reference Series and click on link to ‘The Basics and Beyond’. Follow directions for Transcribing & Translating a Gene. </li></ul>
  7. 7. And more! <ul><li>http:// www.pbs.org/wgbh/aso/tryit/dna/shockwave.html </li></ul><ul><li>www.lewport.wnyric.org/jwanamaker/animations/Protein%20Synthesis%20-%20long.html </li></ul><ul><li>http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302 </li></ul>
  8. 8. And more links <ul><li>http://waynesword.palomar.edu/lmexer3.htm </li></ul><ul><li>☺ Check out the many topics & related articles in the ‘Table of Contents’ </li></ul><ul><li>http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookPROTSYn.html </li></ul><ul><li>http://distance.stcc.edu/BIOL102/Lectures/lesson10/makeprot.htm </li></ul><ul><li>http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossN.html#nucleic acids </li></ul><ul><li>http://workbench.concord.org/web_content/unitV/sickle_cell_worksheet_s.html (a model-based activity to make a sickle-cell mutation) </li></ul><ul><li>http://workbench.concord.org/web_content/unitV/muta_wksht_s.html (a model-based activity to make substitution & deletion mutations) </li></ul><ul><li>http://www.quizmebc.ca/ </li></ul>
  9. 9. Introduction <ul><li>Protein synthesis is the manufacture/synthesis of proteins. </li></ul><ul><li>Occurs in the nucleus and cytoplasm . </li></ul><ul><li>The genetic codes for specific proteins are located on the DNA, e.g. codes for keratin, collagen, Hb, polymer ase , amyl ase , pepsin etc. </li></ul>
  10. 10. Introduction Continued <ul><li>The triplet genetic codes on DNA are called codons . This is a sequence of three DNA bases. </li></ul><ul><li>The site for protein synthesis occurs on the ribosomes (rRNA and protein) in the cytoplasm. </li></ul>
  11. 11. Protein synthesis: divided into 2 processes: <ul><li>(A) Transcription : copying the codons for a protein from a segment of the DNA strand to make mRNA (messenger RNA); requires 2 enzymes ( helic ase , RNA polymer ase ). </li></ul><ul><li>Includes steps of initiation , elongation and termination . </li></ul>
  12. 12. Second Process <ul><li>(B) Translation : translate the sequence of codons for the protein on the mRNA to build a protein at the ribosome; tRNA assists in this process. </li></ul><ul><li>Includes steps of initiation , elongation and termination . </li></ul>
  13. 16. B7– Roles of the Molecules Involved in Protein Synthesis <ul><li>(a) DNA </li></ul><ul><li>Contains the information/ genetic code / triplet codes / codons for the synthesis of proteins, e.g. TCG, ATG, ATT. </li></ul><ul><li>Provides a template for mRNA to be produced. </li></ul>
  14. 18. Let’s draw this together!!
  15. 20. <ul><li>(b) mRNA </li></ul><ul><li>Carries the coded message from the nucleus to the cytoplasm, e.g. codons UAA, CGC, AGU </li></ul><ul><li>Sets the order of amino acids for protein synthesis by the sequence of codons . ( Codon = 3 bases/ nucleotides in a DNA or RNA sequence which specify a single amino acid.) </li></ul>
  16. 22. <ul><li>(c) Ribosomes </li></ul><ul><li>Provides a site for mRNA and tRNA to join together by complementary base pairing. </li></ul><ul><li>Site for protein synthesis (i.e. translation) where it translates mRNA and allows amino acids to bond (peptide bond). </li></ul>
  17. 23. Note: <ul><li>rRNA & protein make up the small and large subunits of ribosomes . The small subunit contains the binding site for mRNA and the large subunit contains 2 binding sites for tRNA ~ amino acid and a dehydration synthesis site! </li></ul>
  18. 24. Remember this!!??
  19. 26. <ul><li>(d) tRNA </li></ul><ul><li>Carries the specific amino acid to the ribosome where its anticodon complementary base pairs with the mRNA codon, e.g. mRNA codon- UUA ; anticodon- AAU . </li></ul>
  20. 30. <ul><li>(e) Amino acids </li></ul><ul><li>These are the monomers of proteins and are picked up by tRNA in the cytoplasm, i.e. tRNA~ amino acids. </li></ul>
  21. 31. Note: <ul><li>mRNA Codon Table (see below) tells what 3 bases on mRNA code for each amino acid (64 combinations of 3 bases) </li></ul><ul><li>Methionine (AUG) on mRNA is called the ‘START codon’ because it triggers the linking of amino acids </li></ul><ul><li>UAA, UGA, & UAG on mRNA signal ribosomes to stop linking amino acids together </li></ul>
  22. 33.       CTT   UCU           TCA     UUU     AUU           TAC     GCU   Amino Acid tRNA Anticodon mRNA Codon DNA Codon
  23. 35. B7– Steps of Protein Synthesis <ul><li>Key words: initiation, elongation, termination, transcription, translation, elongation, DNA, mRNA, tRNA, ribosome, amino acid, triplet code/codons, template, H-bonds, complementary pairing, RNA polymerase, anticodon, peptide bond, polypeptides, dehydration synthesis. </li></ul>
  24. 36. Animations <ul><li>http://highered.mcgraw-hill.com/sites/0072421975/student_view0/chapter24/animations__english_.html </li></ul><ul><li>http://www.pbs.org/wgbh/aso/tryit/dna/index.html# </li></ul><ul><li>(Protein Synthesis activity & animation) </li></ul><ul><li>http://www.lewport.wnyric.org/jwanamaker/animations/Protein%20Synthesis%20-%20long.html </li></ul><ul><li>http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302 </li></ul><ul><li>http://learn.genetics.utah.edu/ </li></ul><ul><li>http://www.eurekacityschools.org/ehs/riggsw/Transcription.ppt </li></ul>
  25. 37. <ul><li>Transcription </li></ul><ul><li>(involves steps of initiation, elongation & termination ) </li></ul><ul><li>Location: nucleus </li></ul><ul><li>Product: mRNA </li></ul><ul><li>Requires 2 enzymes: helic ase and RNA polymer ase . </li></ul>
  26. 42. Here we go….. <ul><li>(a) DNA containing genetic code for protein is in triplet codes. </li></ul><ul><li>(b) Initiation : RNA polymerase initiates transcription by locating and binding to the beginning of a gene/code (i.e. the promoter region ) . </li></ul>
  27. 43. <ul><li>(c) Elongation : - Helic ase unwinds, unzips DNA, breaks H-bonds and provides a template for mRNA formation. </li></ul><ul><li>RNA polymerase travels down the template and complementary base pairs RNA nucleotides with DNA codons forming a mRNA, </li></ul><ul><ul><li>e.g. DNA – CAT; mRNA – GUA. </li></ul></ul><ul><li>RNA polymer ase joins adjacent </li></ul><ul><li>nucleotides to mRNA, forming the S-P-S backbone. </li></ul>
  28. 44. <ul><li>(d) Termination : -RNA polymerase reaches termination sequence at end of gene/code and STOPS mRNA synthesis. RNA polymerase releases the mRNA and detaches from the DNA. </li></ul><ul><li>mRNA exits nucleus through its pores and enters the cytoplasm; DNA rejoins. </li></ul>
  29. 45. Note: <ul><li>mRNA carries a sequence of codons (linear order of three RNA bases complementary to DNA triplet code) to the ribosome… </li></ul><ul><li>One is a “STOP” codon, e.g. UAA, UAG and UGA and a “START” codon, e.g. AUG (Methionine). </li></ul>
  30. 46. <ul><li>2. Translation (involves steps of initiation , elongation and termination ) </li></ul><ul><li>Location: cytoplasm at the ribosome </li></ul><ul><li>Product: protein/polypeptide </li></ul>
  31. 49. Translation <ul><li>(a) tRNAs in the cytoplasm attach the correct amino acid to one end (aided by enzymes). </li></ul><ul><li>(b) Initiation : tRNA~methionine binds to small subunit and this binds to the mRNA. tRNA anticodon (UAC) complementary pairs with mRNA “ START” codon (AUG). Large subunit binds to the small subunit assembling a ribosome. </li></ul>
  32. 50. Translation continued <ul><li>(c) Elongation : -Another tRNA (i.e. tRNA~amino acid) with its anticodon complementary base pairs with mRNA codon on the ribosome. (It has 2 binding sites for incoming tRNA~aa) </li></ul><ul><li>Ribosomes move along one codon to </li></ul><ul><li>receive the next incoming tRNA~aa. </li></ul>
  33. 51. <ul><li>Amino acid undergoes dehydration synthesis and forms a peptide bond. </li></ul><ul><li>“ Empty” or outgoing tRNA will bond with another amino acid in the cytoplasm, i.e. tRNA~aa. </li></ul>
  34. 52. <ul><li>(d) Termination : Synthesis of polypeptide until a “STOP” codon on mRNA (UAA, UAG, UGA). </li></ul><ul><li>Termination of protein synthesis and the polypeptide chain and mRNA are released from the ribosome. </li></ul><ul><li>Ribosome subunits separate. </li></ul>
  35. 53. <ul><li>Ribosomes can synthesize 5-15 peptide bonds/sec! </li></ul><ul><li>Most proteins are 100-200 aa long & takes less than a minute to be synthesized! </li></ul>
  36. 54. <ul><li>http://nobelprize.org/educational_games/medicine/dna/b/translation/translation.html (click on animation icon) </li></ul><ul><li>http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/micro06.swf::Protein%20Synthesis (Great animation) </li></ul><ul><li>http://sps.k12.ar.us/massengale/proteinsynthesis%20ppt.ppt (Nice power points 1 & 2 on Transcrip/lation) </li></ul><ul><li>http://sps.k12.ar.us/massengale/protein%20synthesis2%20ppt.ppt </li></ul>
  37. 59. B7– Problems Using the “Table of mRNA codons” <ul><li>Use the following table to answer questions 1 – 7. </li></ul><ul><li>Note: most of the amino acids are coded with 2, 3 or even 4 different codons. Of these 64 codons , 61 are used to program the 20 amino acids. Three of the 64 codons are used as signals to start or stop the program. </li></ul>
  38. 63. Links <ul><li>http:// learn.genetics.utah.edu / Visit the Genetics Reference Series and click on link to ‘The Basics and Beyond’. Follow the directions for synthesis of a protein. </li></ul>
  39. 64. Ok Let’s Try it Out! <ul><li>1.) What are the RNA triplet codes for Lysine? Leucine? </li></ul><ul><li>using the mRNA table, the codons for Lysine are AAA or AAG. </li></ul><ul><li>using the mRNA table, the codons for Leucine are CUU, CUC, CUA, CUG, UUA and UUG. </li></ul>
  40. 65. <ul><li>2.) What is the DNA triplet code for Tryptophan? </li></ul><ul><li> mRNA = UGG (from table) </li></ul><ul><li>DNA = ACC. </li></ul><ul><li>3.) What are the mRNA triplet codons for “STOP”? </li></ul><ul><li>using the mRNA table, the codons are UAA, UAG and UGA. </li></ul>
  41. 66. <ul><li>4.) The anticodon on a tRNA is GCU. Determine the name of the amino acid and its triplet codon. </li></ul><ul><li>tRNA anticodon GCU would complementary base pair with mRNA CGA at the ribosome. </li></ul><ul><li>using the table, the amino acid code for CGA is Arginine. </li></ul>
  42. 67. <ul><li>5.) DNA contains the following genetic code: TACAAGATT . Determine the amino acid sequence. </li></ul><ul><li>DNA = TAC|AAG|ATT </li></ul><ul><li>mRNA = AUG|UUC|UAA </li></ul><ul><li>= methionine - phenylalanine - stop </li></ul><ul><li>(from table). </li></ul>
  43. 68. B8 – Environmental Mutagens Causing Mutations <ul><li>UV radiation, X-rays, gamma rays. </li></ul><ul><li>Industrial chemicals, e.g. PCB’s, pollutants, pesticides, and food additives, i.e. carcinogens </li></ul><ul><li>Heavy metals such as Lead (Pb), Mercury (Hg). </li></ul><ul><li>Viruses can cause mutations by adding or deleting a nucleotide or by adding a new section of DNA from another organism; (viruses change a proto-oncogene (normal gene) into an oncogene (cancer-causing gene), e.g. HIV. </li></ul>
  44. 69. B8 – DNA Mutations Affecting Protein Synthesis and Possible Genetic Disorders <ul><li>Altering the code for the synthesis of proteins, may result in different codons combining different amino acids with different protein shapes and therefore function is impaired </li></ul><ul><ul><li>(e.g. Sickle-cell anemia causing sickle-shaped RBC’s, cystic fibrosis, muscular dystrophy and other diseases/disorders). </li></ul></ul><ul><li>Also, if the protein is an enzyme, E + S (enzyme + substrate) reaction may not occur or if the protein is a membrane protein, the cell membrane will not function properly. </li></ul>
  45. 70. Three types of gene/DNA Mutations: <ul><li>Deletion </li></ul><ul><li>Addition </li></ul><ul><li>Substitution </li></ul>
  46. 71. 1.) Deletion <ul><li>One or more nucleotides are deleted. </li></ul><ul><li>This alters the code and therefore alters the polypeptide and its function for the cell. </li></ul><ul><ul><li>E.g. Deletion of N-base, Cytosine from codon: </li></ul></ul><ul><li>Normal DNA: TAC|GGG|ATG|TCA| </li></ul><ul><li>Mutation: TA C G|GGA|TGT|CA </li></ul>
  47. 72. 2.) Addition <ul><li>One or more nucleotides are added. </li></ul><ul><li>This pushes all bases back one code and therefore alters the polypeptide and its function for the cell. </li></ul><ul><ul><li>E.g. Addition of an Adenine base to codon: </li></ul></ul><ul><li>Normal DNA: TAC|GGG|ATG|TCA| </li></ul><ul><li>Mutation: A TA|CGG|GAT|GTC|A </li></ul>
  48. 73. 3.) Substitution <ul><li>Involves a change in a single nucleotide and a change in a specific codon. </li></ul><ul><li>When substituting a base the results are variable. </li></ul><ul><ul><li>E.g.1: C substituting for U: </li></ul></ul><ul><li>Normal RNA: UAU = Tyrosine. </li></ul><ul><li>Substitute: UA C = Tyrosine. </li></ul><ul><li>No noticeable effect on these codons as they are both for tyrosine. </li></ul>
  49. 74. <ul><li>E.g.2: G substitute for C: </li></ul><ul><li>Normal RNA: UAC = Tyrosine. </li></ul><ul><li>Substitute: UA G = Stop. </li></ul><ul><li>Drastic effect as UAG is a Stop codon & the resulting protein may be too short and/or unable to function for the cell. </li></ul>
  50. 75. <ul><li>E.g.3: Sickle-cell anemia </li></ul><ul><li>Single base substitution mutation . </li></ul><ul><li>Mutation and triplet code for one amino acid is altered. Glutamate ( CTT or CTC ) is changed to Valine (CAT, CAG, CAA, or CAC). </li></ul>
  51. 77. <ul><li>Normal DNA: ......GGA| CTT </li></ul><ul><li>mRNA: ......CCU|GAA </li></ul><ul><li>Amino acid ….. - Proline - Glutamate . </li></ul><ul><li>Substituting A for T. </li></ul><ul><li> Normal DNA: .......GGA| CTT </li></ul><ul><li> Mutated DNA: ......GGA|C A T </li></ul><ul><li> mRNA: .......CCU|G U A </li></ul><ul><li> Amino acid …… - Proline - Valine. </li></ul>
  52. 78. <ul><li>This alters ONE codon and changes Glutamate to Valine. Their chemical properties differ which causes red blood cells to become abnormally sickle-shaped, causing sickle-cell anemia. </li></ul>
  53. 79. B8 – Mutation Problems Using the “Table of mRNA codons” <ul><li>Use the mRNA table in B7 to answer the following examples of mutation problems. </li></ul><ul><li>1.) The base sequence of a section of DNA is </li></ul><ul><li>A A G C C T G C A. </li></ul><ul><li>Which of the following represents mRNA produced from this DNA after a mutation has occurred? </li></ul><ul><li>a) TTC GGA CGT b) TTC GUU CGT </li></ul><ul><li>c) UUC GGA CGU d) UUC GGA CUU </li></ul>
  54. 80. <ul><li>2.) The DNA strand C G A T G C G A C A T T undergoes a mutation in which the section coding for the amino acid threonine is lost. Which of the following would be the correct codons after this mutation? </li></ul><ul><li>using the table, the codons for threonine are __________, __________, ___________, ___________. </li></ul><ul><li>DNA sequence is CGA /______/______/______ </li></ul><ul><li>mRNA sequence is ______/______/______/______ . </li></ul><ul><li> Now DELETE threonine from the mRNA. Therefore, the correct sequence of codons is </li></ul><ul><li>a. ACG/ CUG/ UAA b. GCU/ ACG/ CUG </li></ul><ul><li>c. GCU/ CUG/ UAA d. GCU/ ACG/ UAA </li></ul>
  55. 81. <ul><li>3.) The following is a DNA base sequence: </li></ul><ul><li>GCA CCT ATA GGA ACC </li></ul><ul><li>Explain any three things that would occur during the translation of this gene if ATA underwent a mutation and was converted to A T T . </li></ul><ul><li>DNA GCA CCT ATA GGA ACC </li></ul><ul><li>Mutated DNA GCA CCT ATT GGA ACC </li></ul><ul><li>mRNA _____ _____ _____ _____ _____ </li></ul><ul><li>amino acid sequence: _____________________________________ </li></ul><ul><li>1.______________________________________ </li></ul><ul><li>2.______________________________________ </li></ul><ul><li>3._______________________________________ </li></ul>