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2013-07-11 01:07:36

ch 10
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  1. How did identification of a gene production begin?
    With mutation
  2. What theory did garrod have?
    One gene: one enzyme
  3. How does a mutant phenotype arise?
    It arises from a change in the protein’s amino acid sequence
  4. What is the one gene:one enzyme relationship referred to as now
    One gene: one polypeptide
  5. What is molecular biology?
    The study of nucleic acids and proteins; it also focuses on gene expression
  6. What are two ways that gene expressions form a specific polypeptide
    Transcription and translation
  7. What is transcription
    It copies information from a DNA sequence (gene) to a complementary RNA sequence
  8. What is translation
    It converts RNA sequence to amino acid sequence of a polypeptide.
  9. What are the three kinds of RNA in protein synthesis
    mRNA, rRNA and tRNA
  10. What is mRNA
    It is messenger RNA and it transcripts; it carries a copy of dna sequence to the site of protein synthesis AT THE RIBOSOME
  11. What is rRNA?
    It is ribosomal RNA and translation. It catalyzes peptide bonds between amino acids
  12. What is tRNA
    Transfer RNA mediates between mRNA and protein. It carries amino acids for polypeptide assembly.
  13. What components does transcription require?
    A dna template, nucleoside triphosphates (ATP, GTP, CTP, UTP) as substrates and an RNA polymerase enzyme
  14. What are the types of RNA produced by transcription
    tRA, rRNA, mRNA, smaller nuclear RNA (snRNA’s), micro RNA’s (miRNA)
  15. what does RNA polymerases do
    it catalzes synthesis of RNA from DNA template
  16. What is different about RNA polymerases in respect to DNA polymerases?
    RNA polymerases DO NOT need primers
  17. What are the 3 phases of transcription
    Initiation, elongation, and termination
  18. What does initiation require and what does it tell you
    It requires a promoter that tells you WHERE to start and WHICH STRAND to transcribe
  19. What happens in Elongation?
    RNA unwinds DNA 13 BASE PAIRS AT A TIME, READS TEMPLATE 3-TO-5, ADDS NUCLEOTIDES TO 3’, the first nucleotide in the NEW RNA is its 5’ end. RNA polymerase can proofread but it allows more mistakes
  20. What happens in Termination
    A specific DNA base sequence is required. Sometimes, the transcript needs a helper protein and other times it falls away from dNA template and RNA polymerase.
  21. What are coding regions?
    Sequences of DNA molecules that are expressed as proteins.
  22. What are 2 types of coding regions?
    Introns (intervening regions) and exons (expressed regions)
  23. What are introns
    Noncoding sequences
  24. What are exons
    Coding sequences
  25. Where do Introns and Exons appear?
    In the primary mRNA transcript- pre-mRNA. And introns are removed from the final mRNA.
  26. What is nucleic acid hybridization
    It reveals introns. The target DNA is denatured and incubated with a probe (nucleic strand) and they join creating hybrid strand. (strand and a half)
  27. What do introns do
    They interrupt but do not scramble the DNA sequence that encodes a polypeptide
  28. What can separated exons do
    They can code for different domains of the protein
  29. What does the spliceosome do
    It’s a protein complex that cuts of pre-mRNA, releases introns and splices the exons together to produce the mature mRNA ready to go on to the next protein making step
  30. What happens in B-thalassemia
    The pre-mRNA can not be spliced correctly.
  31. What does alternative splicing result in
    Different mRNAs and different polypeptides from a single gene
  32. What does the genetic code do
    It specifies WHICH amino acid will be used to build a protein
  33. What is a codon
    It is a sequence of 3 bases, each specifying a particular amino acid
  34. What is the universal START codon
    AUG- initiation signal for translation
  35. What are the stop Codons-
    UAA, UAG, UGA. They stop translation and the polypeptide is released.
  36. What is a redundant genetic code
    When there is more than one codon for a particular amino acid
  37. Why are genetic codes not ambiguous
    Each codon specifies only one amino acid
  38. What is meant by ‘genetic code is universal’
    The condons all specify the same amino acids in all organisms.
  39. What are some exceptions the the ‘universal genetic code’ idea
    Mitochondria, protists, and chloroplasts
  40. How can mutations be defined
    In terms of their effects on polypeptide sequences.
  41. What are silent mutations
    Mutations that have no effect on amino acids. They are found in noncoding regions of DNa
  42. How do base substitutions affect amino acid sequence
    SOMETIMES they affect the sequence, sometimes they don’t and it may be repaired.
  43. What is missense mutation
    There are substitutions by ONE amino acid for another protein.
  44. What can be a result of missense mutations
    A defective protein or reduced protein efficiency or even gain of function
  45. What is nonsense mutation
    STOP that nonsense. A base substitution causes a STOP CODON somewhere in the mRNA so it is stopped prematurely. So much so that it may not even have a function
  46. What is a frameshift mutation?
    Insertions or deletions of bases in DNA, leaving an extra nonfunctional protein. Poor A is all alone :(
  47. What does tRNA do to mRNA
    It links info in the codons with specific amino acids.
  48. For each amino acid, there is a ____ of tRNA
    Specific type or ‘species’
  49. In what ways can we ensure the protein made is the one specified by mRNA?
    tRNA must read mRNA codons correctly & tRNAs must deliver amino acids corresponding to each codon.
  50. What are the 3 functions of tRNA
    Bind to amino acid and charge it, bind to their midpoint-anticodon-to mRNA molecules & interact with ribosomes.
  51. What does wobble do
    When the codon is not specified for the base at the d’ end, the wobble allows each cell to produce fewer tRNA species without making the genetic code ambiguous but specific
  52. What charges the tRNA with amino acids
    Aminoacyl-tRNA synthases; activating enzymes
  53. What is the amino acid to tRNA ratio?
  54. Which would be recoginized? Amino acid or tRNA in protein synthesis?
    Protein synthesis machinery recognizes anticodon, not amino acid
  55. Where does translation of mRNA by RNA happen?
    At the workbench: the ribosome. It holds mRNA and charged tRNAs in correct position to allow assy of polypeptide chain.
  56. Are ribosomes specific?
    No! they can make ANY type of protein!!
  57. 3 binding sites in the large subunit.
    A, P, and E
  58. The A site
    Amino site, binds with anticodon of charged tRNA
  59. The P site
    Polypeptide site; tRNA adds amino acid to growing chain
  60. E site
    Site where tRNA sits before being released from ribosome
  61. What are 3 steps of translation?
    Initiation, elongation, and termination
  62. What is initiation in transcription?
    Charged tRNA and small ribosomal subunit bound to mRNA make up an initiation complex. The small subunit moves along mRNA until they get to the start codon, AUG. first amino acid Is ALWAYS methionine. The large subunit joins complex and charge tRNA is now at the P site
  63. What happens during elongation in transcription
    Second charged tRNA enters A site, large subunit (hand) catalyzes two reactions (breaks bond between tRNA in P site and ITS amino acid. A Peptide bond forms between amino acid and amino acid on tRNA in the A site.
  64. How do we get from elongation to termination in transcription?
    The first tRNA has released its methionine and it moves to the E site and leaves ribosome where it can be charged again. This happens again and again.
  65. What is peptidyl transferase activity?
    It is something the large subunit has. If rRNA is destroyed, the activity stops.
  66. What happens during termination in transcription
    Translation ends with a stop codon enters A site. It binds a protein release factor and allows for hydrolysis between polypeptide chain and tRNA on P site. Chain separates from ribosome & c terminus is last Amino acid added.
  67. What is a polyribosome (polysome)
    A strand of mRNA with associated ribosomes
  68. What are two posttranslational askects of protein synthesis
    Polypeptide emerges from ribosome and gets into 3d shape. Its conformation lets it interact with others. It may contain a signal sequence that lets you know wherein the cell it belongs
  69. What happens when there is no signal sequence?
    The protein will stay where it was made.
  70. How do signal sequences work?
    They bind to a receptor protein on the organelle surface, a channel is formed and the protein moves into the organelle.
  71. What are some types of protein modifications?
    Proteolosys, glycosylation, phosphorylation
  72. What is proteolysis
    Cutting of a long polypeptide chain into final products by proteases
  73. What is glycosylation
    Addition of carbohydrates to form glycoproteins
  74. What is phosphorylation
    Addition of phosphate groups catalyzed by protein kinases.
  75. What are protein kinases
    Charged phosphate groups that change the conformation of the protein
  76. How do antibacterials target bacterial protein synthesis?
    They kill bacteria by interrupting translation. They bind to small subunit of ribosome which changes its structure and then the poor charged tRNA can’t bind to A site :(