Biology 1115 Chapter 17

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  1. Proteins are the links between _________ and ____________.
    genotype and phenotype
  2. What is a gene?
    a region of DNA that can be expressed to produce a final functional product, wither a polynucleotide or an RNA molecule.
  3. What is gene expression? What are the two stages?
    • the process by which DNA directs protein synthesis
    • includes two stages: transcription and translation
  4. RNA is the ___________ between genes and the proteins for which they code.
  5. What is transcription and what does it produce?
    • is the synthesis of RNA under the direction of DNA
    • produces messenger RNA (mRNA)
  6. What is translation and where does it take place?
    • synthesis of polypeptide, which occurs under the direction of mRNA
    • takes place in the ribosomes
  7. What is the central dogma?
    • concept that cells are governed by a cellular chain of command
    • DNA-->RNA-->protein
  8. What happens to mRNA produced by transcription in Prokaryotes?
    it's immediately translated without more processing
  9. In eukaryotic cell, what separates transcription and translation?
    nuclear envelope
  10. What is a primary transcript?
    the initial RNA transcript from any gene (pre-mRNA)
  11. Define triplet code.
    series of non-overlapping, three nucleotide words
  12. How many possible codons are there?
  13. During transcription, what does the template strand do?
    provides a template for ordering the sequence of nucleotides in an RNA transcript
  14. What bond is formed between the amino acids?
    peptide bonds
  15. During translation, the mRNA base triplets, called ___________, are read in the _______ direction.
    • codons
    • 5' to 3' direction
  16. What happens in RNA synthesis and what is catalyzed by?
    catalyzed by RNA polymerase, which pries opens the DNA strands apart and hooks together the RNA nucleotides
  17. What direction is DNA synthesized?
    5' to 3'
  18. What direction is mRNA read for translation?
    5' to 3'
  19. What direction is the DNA template strand read?
    3' to 5'
  20. What direction is mRNA transcript synthesized?
    5' to 3'
  21. The DNA sequence where RNA polymerase attaches is called ___________.
    the promoter: signals the initiation of RNA synthesis
  22. what is the TATA box?
    a nucleotide sequence that is crucial in forming the initiation complex in eukaryotes
  23. What are the 2 functions of transcription factors?
    they settle the binding of RNA polymerase and the initiation of transcription
  24. What is the transcription initiation complex?
    complete assembly of transcription factors and RNA polymerase 2 bound to a promoter.
  25. What is the function of RNA polymerase in transcription?
    moves along the DNA, it untwists the double helix
  26. In bacteria, how does termination occur?
    In bacteria, the polymerase stops transcription at the end of the terminator.
  27. In eukaryotes, how does termination occur?
    In eukaryotes, proteins associated with the RNA transcript cut it free from the polymerase, the polymerase eventually falls off the DNA.
  28. Enzymes in the eukaryotic nucleus _____________ before the genetic messages are dispatched to the cytoplasm.
    modify pre-mRNA
  29. How is each end of a pre-mRNA molecule modified before being dispatched to the cytoplasm? (2)
    • 5' end receives a modified nucleotide 5' cap
    • 3' end get a poly-A tail
  30. What functions to theses modifications provide for the pre-mRNA? (3)
    • facilitate the export of mRNA
    • protect mRNA from hydrolytic enzymes
    • help ribosomes attach to the 5' end
  31. What are non-coding regions in the RNA transcripts called?
    intervening sequences or introns
  32. What are the regions of RNA transcript that are usually expressed/ translated into amino acid sequence called?
  33. What is RNA splicing?
    removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence.
  34. What is alternative RNA splicing?
    some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during RNA splicing.
  35. What does alternative RNA splicing produce?
    the number of different proteins an organism can produce is much greater than its number of genes
  36. In many cases different exons code for the _____________ in a protein.
    different domains
  37. What may result in the evolution of new proteins?
    exon shuffling
  38. What are ribozymes?
    catalytic RNA molecules that function as enzymes and can splice RNA
  39. What are the 3 properties of RNA that enable it to function as a n enzyme?
    • it can form a three-dimensional structure because of its ability to base pair with itself
    • some bases in RNA contain function groups
    • RNA may hydrogen-bond with other nucleic acid molecules
  40. A cell ____________ an mRNA message into protein with the help of ____________.
    • translates
    • transfer RNA (tRNA)
  41. What makes the molecules of tRNA unique? (2)
    • each carries a specific amino acid on one end
    • each has an anticodon on the other end
  42. What does anticodon do?
    it base-pairs with a complementary codon on mRNA
  43. What does tRNA consist of?
    a single RNA strand that is about 80 nucleotides long
  44. What are the two steps to accurate translation?
    • first: correct match between a tRNA and an amino acid done my the enzyme aminoactyl-tRNA synthase
    • second: a correct match between the tRNA anticodon and mRNA codon
  45. What is wobble?
    flexible paring at the third base of a codon, which allows some tRNAs to bind to more than one codon
  46. What is the function of ribosomes in protein synthesis?
    facilitate specific coupling of tRNA anticodons with mRNA codons in protein synthesis
  47. What are the two ribosomal subunits made of?
    proteins and ribosomal RNA
  48. What are the 3 binding sites for tRNA in order?
    • A site: holds the tRNA that carries the next amino acid to be added to the chain
    • P site: holds the tRNA that carries the growing polypeptide chain
    • E site: exit site, where discharged tRNAs leave the ribosome
  49. Each addition of amino acids involves proteins and elongation factors and occurs in three steps:
    • codon recognition
    • peptide bond formation
    • translocation
  50. How does termination in translation occur? (2)
    • termination occurs when a stop codon in the mRNA reaches the A site of the ribosome
    • A site accepts a proton called a release factor, which causes the addition of a water molecule instead of an amino acid
  51. What is mutations?
    changes in the genetic material of a cell or virus
  52. What mutations occur during DNA replication, recombination or repair?
    spontaneous mutations
  53. What are mutagens?
    physical or chemical agents that can cause mutations
  54. What are point mutations?
    chemical changes in just one base pair of a gene
  55. What are the two main categories that point mutations are divided into?
    • base-pair substitutions
    • base-pair insertions or deletions
  56. What is silent mutation?
    have no effect on the amino acid produces by a  codon because of redundancy in the genetic code
  57. Which mutation still codes for an amino acid, but not necessarily the right amino acid?
    missense mutation
  58. What is a nonsense mutation?
    change an amino acid into a stop codon, nearly always leading to a non-functional protein
  59. What are the three mutations in base-pair substitutions?
    • silent mutation
    • missense mutation
    • nonsense mutation
  60. Insertion or deletion of nucleotides may alter the reading frame, producing what?
    frame shift mutation
  61. what will a single nucleotide insertion close to the start of the coding sequence cause?
    frameshift mutation, immediate nonsense
  62. What will a single nucleotide deletion near the end of a coding sequence cause?
    frameshift mutation, extensive missense
  63. What will a deletion of three nucleotides near the middle of a gene cause?
    no frameshift, but one amino acid missing
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Biology 1115 Chapter 17
2013-11-05 04:53:18

Genetics: from gene to protein
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