Chapter 17

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Chapter 17
2012-12-10 15:01:40
BI 253

Ch 17 12-10-12
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  1. ___ are defined as sequences of DNA & are expressed as physical characteristics called ____.
    • Genes
    • Phenotypes
  2. Phenotypes are defines by ____.
  3. Phenotypic differences are the result of differences in ___ ___.
    Specific Proteins
  4. What 1940s team formulated the hypothesis "one gene, one enzyme?"
    Beadle & Tatum
  5. The "one gene, one enzyme" hypothesis actually means "one gene, one ____."
  6. Explain "one gene, one enzyme" hypothesis.
    Mutations have simple effects & each mutation causes a effect in only 1 enzyme in a metabolic pathway
  7. Who created the Central Dogma of Molecular Biology?
    Francis Crick
  8. What is the main premiss for Central Dogma?
    DNA codes for RNA, RNA codes for protein
  9. What were Crick's 2 questions of his hypothesis?
    • How does info get fr nucleus to cytoplasm?
    • How does a DNA sequence get transformed into a specific AA sequence of a polypeptide?
  10. What did Crick propose to ans "How does info get fr nucleus to cytoplasm?"
    He proposed messenger hypothesis & transcription
  11. What did Crick propose to ans "How does DNA sequence get transformed into specific AA sequence of a polypeptide?"
    He proposed the adapter hypothesis & translation
  12. What term describes when mRNA travels fr nucleus to cytoplasm where it serves as template for synthesis of protein?
  13. What term is given to a process where an adaptor molecule that can bind to a specific AA & recognize a sequence of nucleotides then translate language of DNA into language of proteins?
  14. ____ are the adaptor molecules in translation.
  15. What does tRNA do in translation?
    Recognizes genetic message of mRNA & carry specific AAs to form the polypeptide chain
  16. Reverse transcription is the exception to ____ ____.
    Central Dogma
  17. Retroviruses utilize ___ rather than ___ as their genetic material.
    • RNA
    • DNA
  18. What do RNA retroviruses do w/RNA?
    Convert it to a DNA copy inside a host cell & then use it to make more RNA
  19. What enzyme is utilized by RNA retroviruses to accomplish reverse transcription?
    Reverse Transcriptase
  20. What 3 things are required for transcription?
    • DNA template
    • Ribonucleoside Triphosphates (ATP,GTP,CTP & UTP)
    • Enzyme - RNA Polymerase
  21. What 3 RNAs are made in transcription?
    • mRNA
    • tRNA
    • rRNA
  22. What are the 3 steps in transcription?
    • Initiation
    • Elongation
    • Termination
  23. What does RNA polymerase look like?
    Crab Claw
  24. How does RNA polymerase work?
    Binds to special sequence of bases in DNA template, pincers close
  25. What are the 3 ways RNA differs fr DNA?
    • RNA is single stranded rather than double
    • Sugar is ribose rather than deoxyribose
    • RNA utilizes Uracil rather than Thymine
  26. RNA polymerases do not require a ___ like DNA polymerases.
  27. Transcription requires a promoter at initiation which is what?
    Special sequence of DNA to which RNA polymerase binds to very tightly
  28. Define the initiation site.
    Part of the promoter sequence where transcription begins
  29. Prokaryotic promoters are (different/the same as) Eukaryotic promotors.
  30. The part of transcription where the RNA strand is made is called ____.
  31. What 3 things does an RNA polymerase accomplish during Elongation?
    • Unwinds DNA, approx 10 base prs @ a time
    • Reads template in 3' → 5' direction
    • New RNA elongates fr its 5' end → 3' end
  32. What is the time when transcription stops called and where does it stop?
    Termination at the termination site
  33. What is located at the termination site of transcription?
    Certain base sequences in DNA that specify termination
  34. What 2 things can happen @ transcription termination, depending on the gene?
    • New transcript simply falls away fr DNA template & RNA polymerase
    • A helper protein pulls transcript away
  35. Where does pre-mRNA come into play?
    @ post transcriptional processing
  36. What are 3 characteristics of pre-mRNA?
    • RNA produced @ end of transcription
    • Has a lot of "non-coding" regions
    • Will be modified to produce mRNA that will later be used to make protein
  37. In post transcriptional processing, what is the name given to non-coding regions (junk nRNA) that will be removed fr pre-mRNA called?
  38. Coding regions that make up final mRNA template in post transcriptional processing are called ____.
  39. Transcription is carried out by ____ ____ and creates RNA fr DNA.
    RNA Polymerases
  40. Translation is performed on ____ & creates polypeptides fr RNA.
  41. Replication is carried out by ___ ___.
    DNA Polymerases
  42. Reverse transcription copies ___ → ___.
    RNA → DNA
  43. The sequence of bases in a gene that specify the amino acid sequence of a protein is known as the ___ ___.
    Genetic Code
  44. A triplet of nucleotide bases that code for a specific amino acid is called a ___.
  45. There are __ possible codons & the code for __ amino acids & start & stop codons.
    • 64
    • 20
  46. What start codon is the initiation signal for translation?
    AUG - methionine
  47. A ___ ___ directs ribosomes to end translation.
    Stop Codon
  48. What is meant by "The genetic code is redundant but not ambiguous?"
    There can be more than 1 codon for a single AA (redundant) however each codon codes for ONLY 1 AA (unambiguous)
  49. What enzymes charge tRNAs w/AA's?
    Activating Enzymes
  50. Each activating enzyme is specific for 1 ___ ___ & its ___.
    • Amino Acid
    • tRNA
  51. Activating Enzymes have a 3-part active site that binds what 3 things?
    Specific AA, ATP & a specific tRNA
  52. What are the 3 functions of Crick's Adaptor Molecules?
    • Carries AAs & binds to specific tRNA molecule
    • Assoc w/mRNA via codon-anticodon interactions
    • Interacts w/ribosomes to form polypeptides
  53. 3 bases that are complimentary to an mRNA codon is called what?
  54. T or F: Each tRNA species has a unique anticodon.
  55. What are 2 characteristics of an Amino Acid binding site?
    • It is located at 3' end
    • Location where specific AA covalently bonded
  56. What structure holds mRNA & charged tRNAs in the rt positions & is considered to be "the workbench" of translation?
  57. What is the function of the ribosome small subunit?
    It validates the codon - anticodon match
  58. The ribosome lg subunit has 3 sites that bind ___.
  59. What are the 3 sites that that bind tRNAs on a lg ribosome subunit?
    • The A (amino acid) site
    • The P (polypeptide) site
    • The E (exit) site
  60. Which site on lg ribosome subunit is where a charged tRNA anticodon binds to the mRNA codon?
    The A (amino acid) site
  61. The site where the tRNA adds its amino acids to the polypeptide chain is the what?
    The P (polypeptide) site
  62. The "E" or exit site is where what happens?
    The "empty" tRNA hangs out waiting to be released
  63. When ribosomes are not translating, what happens to the 2 subunits?
    They separate
  64. The sm ribosome subunit is located where on a strand of RNA?
    On the top side
  65. The lg ribosome subunit is located where on a strand of RNA?
    On the same side as the codons
  66. What is the process that transforms the RNA fr transcription to a specific amino acid sequence of a polypeptide?
  67. What are the 3 steps in the process of translation?
    • Initiation
    • Elongation
    • Termination
  68. What happens during the initiation phase of translation?
    • 1st the sm subunit of ribosome binds to ribosomal binding sateen the 5' side of actual start codon
    • 2nd the lg subunit joins the complex
  69. The start codon in translation is ___ & the appropriate anticodon is ___.
    • AUG - methionine
    • UAC
  70. During initiation of translation, the start codon AUG arrives attached to what?
    A charged tRNA
  71. What are the 4 steps in the elongation process of translation?
    • Charged tRNA enters open A site
    • Lg subunit then breaks bond between tRNA in P site & its AA & forms a bond between new AA & 1 attached to tRNA in the A site
    • 1st RNA releases its methionine & moves to E site & is dissociated fr ribosome
    • 2nd tRNA shifts to P site as ribosome moves 1 codon along mRNA (5' → 3')
  72. In the initiation phase of translation, what site does the AUG bind too?
    The P (polypeptide) site
  73. The elongation phase of translation begins at what site in the lg subunit?
    The "A" (amino acid) site
  74. When a stop codon binds at the A site what happens?
    • It binds to a protein release factor which breaks the bond between the polypeptide chain & the tRNA in the "P" site
    • New protein separates fr the ribosome & ribosome falls away fr mRNA
  75. ___ are heritable changes in genes that involve alterations to DNA nucleotide sequence.
  76. ___ mutations are mutations of a single nucleotide.
  77. A ____ mutation changes the position or orientation of a DNA segment w/o removing any genetic info or may cause a segment of DNA to be lost or duplicated.
  78. What are the three types of point mutations?
    • Silent
    • Missence
    • Nonsense
  79. A point mutation that results in no change in amino acids in the protein when altered mRNA is translated is called what?
    Silent mutation
  80. The type of point mutation that causes an amino acid substitution & could cause a disease such as sickle cell anemia is called what?
    Missence Mutation
  81. Explain the nonsense type of point mutation.
    A base substitution causes a stop codon to form in the mRNA resulting in a nonfunctional shortened protein
  82. What are the 4 types of chromosomal mutations?
    • Deletions
    • Duplications
    • Inversions
    • Translocations
  83. In a deletion type of chromosomal mutation what happens?
    A piece of DNA molecule breaks @ 2 pts & when 2 pieces rejoin a section is left out
  84. The chromosomal mutation where 1 chromosome has double the amt of a particular section is a ___ mutation.
  85. How does a duplication mutation occur?
    Homologous chromosomes break at different positions & reconnect to the wrong partners
  86. A chromosomal mutation where a portion of the chromosome has broken off, turned upside down & reattached is called a ____ mutation.
    Inversion Mutation
  87. A chromosomal mutation where a portion of a chromosome breaks off & is inserted into another chromosome is called a ____ mutation.
    Translocation Mutation
  88. What is 1 example of an abnormality caused by a translocation mutation?
    Down Syndrome
  89. What is the difference between spontaneous mutations & induced mutations?
    A spontaneous mutation causes permanent changes w/o outside influence whereas an induced mutation involves permanent changes caused by an outside agent.
  90. What are 2 causes of spontaneous mutations?
    • Errors in replication
    • Nondisjunction
  91. What is the cause of induced mutations?
    Mutagens such as chemicals or radiation