biochem 012 DNA and protein synthesis part 4 (watson crick griffith chargoff's rule translation

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mikepl103
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biochem 012 DNA and protein synthesis part 4 (watson crick griffith chargoff's rule translation
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2014-12-04 12:47:08
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biochem 012 DNA protein synthesis part watson crick griffith chargoff rule translation ribosomes mRNA 26
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biochem 012 DNA and protein synthesis part 4 (watson, crick, griffith, chargoff's rule, translation, ribosomes, mRNA) #26
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  1. what is a ribozyme?
    ribozymes are catalytic RNA molecules that function as enzymes and can splice RNA
  2. what are introns?
    most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that lie between coding regions called introns
  3. what is RNA splicing?
    RNA splicing removes introns and joins  exons, creating an mRNA molecule with a continuous coding sequence
  4. what are splicosomes? what are they used for?
    splicosomes consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recongnize the splice sites in mRNA. In some cases, RNA splicing is carried out by spliceosomes
  5. true or false? all biological catalysts are proteins.
    false, ribozomes are catalytic molecules as well
  6. what are the three properties of RNA that enable it to function as an enzyme?
    • 1. it can form a three-dimensional structure because of its ability to base pair with itself
    • 2. Some bases in RNA contain functional groups
    • 3. RNA may hydrogen-bond with other nucleic acid molecules
  7. what is the functional and evolutionary importance of introns?
    some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during RNA splicing--such variations are called alternative RNA splicing. Because of alternative splicing, the number of different proteins an organism can produce is much greater than its number of genes.

    Proteins often have a modular architechture consisting of discrete regions called domains. In many cases, different exons code for the different domains of a protein. Exon shuffling may result in the evolution of new proteins
  8. in what two ways are tRNA molecules not identical
    • 1. each carries a specific amino acid on one end
    • 2. Each has an anticodon on the other end; the anticodon basepairs with a complementary codon on mRNA
  9. tRNA's two dimensional structure resembles what? what about its three-dimensional structure?
    clover leaf; L-shaped
  10. accurate translation requires that the tRNA has two properties:
    • 1. a correct match between a tRNA and an amino acid, done by the enzyme aminoacyl-tRNA synthetase
    • 2. a correct match between the tRNA anticodon and an mRNA codon
  11. what is the enzyme that matches each tRNA with its corresponding amino acid?
    aminoacyl-tRNA synthetase
  12. what is wobble?
    flexible pairing at the third base of a codon is called wobble and allows some tRNAs to bind more than one codon
  13. the two ribosomal subunits (large and small) are made of what?
    proteins and rRNA
  14. what are the three binding sites for tRNA on the ribosome?
    P site, A site, and E site
  15. describe the P site
    it holds the tRNA that carries the growing polypeptide chain
  16. describe the A site
    it holds the tRNAthat carries the next amino acid to be added to the chain
  17. describe the E site
    it is the exit site, where discharged tRNAs leave the ribosome
  18. what are the three stages of translation?
    initiation, elongation, and termination
  19. all three stages require ___ ____ that aid in the translation process
    protein factors
  20. During the elongation of the polypeptide chain in ribosomes, each addition of an amino acid involves proteins called ________ ____ and occurs in what three steps?
    elongation factors; the three steps are: codon recognition, peptide bond formation, and translocation
  21. termination occurs when a ____ ____ in the mRNA reaches the __ _____ of the ribosome
    stop codon; A site

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