LEC16 - Haw many loops when mRNA hybridized to genomic DNA...

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Haw many loops when mRNA hybridized to genomic DNA?
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Which of the following is found in exon 2? A. AUG for protein start site B. Part of the 3’ splice site for intron 1 C. Part of the 5’ splice site for intron 2 D. All of the above
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24 exons, 4 are variable Protein has dual function: antibody and neural patterning in the brain
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1. U1 snRNP binds to 5’ splice site via base pairing with the U1 RNA Spliceosome Formation
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2. Binding U2 snRNP to branch point Critical A bulge
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U1 and U2 bound to pre-mRNA
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3. U4/U5/U6 join to form pre-catalytic spliceosome 4. Release of U1 & U4 yields catalytic spliceosome
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Figure 14-5
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The intron is released as a lariat. The spliceosome dissociates and the mRNA is ready to be transported out of the nucleus 5’ exon 3’ exon Intron (lariat) 7mG AAAAA n
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In some rare instances, introns can splice themselves out of the RNA Intron folds into a 3D shape Catalyzes its own splicing Introns may have originated as self- splicing segments but later evolved to require snRNPs
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Why do eukaryotes have introns while prokaryotes don’t? Two theories: Introns early model: Introns existed in all organisms and were later lost in prokaryotes so they could replicate faster Introns late model: Introns evolved later by insertion of self-splicing elements similar to transposable elements
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  • Winter '12
  • Lin
  • DNA, splice site, Introns early model

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