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24 Cards in this Set
- Front
- Back
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RNA splicing is executed by? what is it made out of? |
spliceosome, made out of snRNPs (small nuclear ribonucleoprotein particles) |
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describe nuclear pre-mrna splicing (their introns specifically) |
their introns contain short consensus sequences that mark exon-intron boundaries, splicing done by spliceosome |
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describe self-splicing introns |
can splice without other proteins, two classes: group I and group II introns (group II related to nuclear introns) |
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Whats different about yeast tRNA splicing compared to other types of splicing? |
cleavage and ligation reactions are seperate unlike other types of splicing |
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what is the GU-AG rule? |
where each intron will be cut at each end, they almost always have a GU at the 5'end and a AG at the 3'end |
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how are exons correctly joined? |
because introns will only be taken out through 5' GU and AG-3' splice sites which are interchangeable |
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are introns removed randomly? |
no they are removed in a specific order |
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what is step 1 in Nuclear mRNA precursor splicing? |
cut at 5'splice site seperating left exon from right intron-exon RNA lariat is formed by the 2'OH of A attacking the phosphate group of the G on the same intron and linking them via a phosphodiester bond |
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what is step 2 in Nuclear mRNA precursor splicing? |
cut is made at 3'splice site, intron is released and right exon join left exon 3' OH of exon 1 attacks the phosphodiester bond between intron and exon 2, which yields the spliced exon1/2 and the lariet shaped intron |
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what are the roles of snRNPS in splicing? |
they make up the splicesome, they recognize the 5'splice site and the branch site and are able to bring these two sites together. they also catalyze the RNA cleavage and joining reactions |
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what are the recognition events for pre-mRNA intron by RNAs and proteins? |
U1 recognizes 5'splice site, then replaced by U6 U2-association factor- recognizes the 3' splice site U2 recognizes the branch point U5 binds to the 5' and 3' -splice sites after initial recognition by other factors, bringing the ends (the 2 exons) together |
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describe U1 snRNP |
its 8 proteins + U1 snRNA, bp between 5'splice site and u1 is required for splicing and spliceosome assembly |
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what did the U1 mutational analysis test show? |
that complementarity between U1 snRNA and 5'splice is necessary for splicing ie. U1 snRNA pairs with 5'splice sites at specific nucleotide positions |
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what is the E complex? |
E (early pre-splicing complex)- U1 snRNP pairs with 5'splice site U2AF splicing factor binds to Py tract downstream of branch site, close to the 3' splice site |
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what is the A complex? |
A (pre-splicing) complex: ATP hydrolysis U2 snRNP pairs with intron branch site (A not paired) |
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what is the B1 complex? |
B1 complex is - U5/U4/U6 snRNPS binds, U5 binds 5' exon splice site |
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Describe U2/U6 splicing? |
U6 and U4 snRNAs are paired before joining spliceosome U4s goal is to isolate U6 until needed releasing U4 allows U6 to change conformation to bind to U2 Once U6 binds U2 resulting RNA structure catalyzes splicing |
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what is the B2 complex? |
U1 release causes repositioning: U5 at exon -> intron, U6 binds 5' splice site |
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What is the C1 complex? |
ATP hydrolysis U4 release triggers U2/U6 catalyzed transesterification U5 binds 3' splice site 5' site is cleaved resulting in 5'-2' lariat (A in branch site attacks 5' splice site) |
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what is the C2 complex? what protein removes spliced mRNA from the spliceosome and disassembles the spliceosome? |
ATP hydrolysis again and spliceosome complex moves for exon-exon transesterification, ligating exons and releasing introns in vivo, Prp22 The lariat is rapidly degraded |
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what does the RNA polymerase II CTD do in splicing? |
assists assembly of splicing factors |
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why are introns maintained if they are constantly being spliced? |
exon shuffling |
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whats one outcome of alternative splicing events? what proteins are involved? |
it can determine the sex of a fruit fly, Tra and Tra-2 are SR proteins that contribute to female specific splices |
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who won the nobel prize for pluripotent cells? |
Shinya Yamanaka |
