GDCB 511 5_1_09 REVIEW _Exam 4 %26 Final(2nd part)_YANG

GDCB 511 5_1_09 REVIEW _Exam 4 %26 Final(2nd part)_YANG -...

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GDCB 511, May 1, 2009 Announcements Both Exam 4 and the Final will be held at 7:30— 9:30 AM, Tuesday, May 5, Atanasoff Hall B29 7:30-8:30, Exam 4=100 points 8:30-9:30, Final=100 points (50 +50)
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Overview of splicing reactions
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Overview of snRNA associations U1 base pairs with the 5’ splice site U2 base pairs with the conserved sequence at the splicing branchpoint U4 base pairs with U6 U6 base pairs with the 5’ splice site; U6 also base pairs with U2 U5 associates with the last nucleotide in one exon and the first nucleotide of the next, presumably lining up the exons for splicing
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Compare cis-splicing (left) Vs. trans-splicing (below).
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What is the mechanism of RNA editing? 1. Nuclease detects mis- match and cuts pre-mRNA at site of non-base pairing. 2. The mismatched “U” residue in the pre-mRNA can be excised by a 3’ RNA exonuclease; or, a “U” residue can be added by TUTase (terminal uridylyl transferase) 3. The cut is resealed by RNA ligase. Editing proceeds from 3’ to 5’ until the entire mRNA is edited.
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Figure 15.26 Factors involved in 3’ end formation and polyadenylation CPSF: Cleavage and polyadenylation specificity factor that binds AAUAAA signal; CstF: Cleavage stimulation factor that binds downstream G/U-rich region; CF I/ CF II: Cleavage factors that cut RNA transcript; PolyA polymerase (PAP): catalyzes polyA synthesis; PolyA Binding protein II (PABII): Binds growing polyA tail and stimulates polyA addition.
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Cleavage in mammals requires several proteins CPSF – cleavage and polyadenylation specificity factor CstF – cleavage stimulation factor CF I – Cleavage factor I CF II – Cleavage factor II Poly (A) polymerase RNA polymerase II
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lin-4, let-7 C.  elegans animal pre- miRNAs plant pre-miRNAs miRNAs are derived from primary transcripts (pri-miRNAs) that form stem-loop structures with the miRNA in a base paired region. Most miRNA genes are located in a different part of genome than their target mRNA. But some are encoded in an intron of their target mRNA.
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Fig. 16.45 MicroRNAs regulate gene expression. First discovered in C. elegans , microRNAs are now known to be important regulators of gene expression in animals and plants. They act by blocking translation (animals) or triggering the RNAi pathway (plants).
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Mechanisms of chromosomal DNA replication in bacteria and bacteriophage Basic Features: 1. Template copied via complementary basepairing (proposed by Watson &Crick, 1953) 2. Semi-Conservative: Meselson and Stahl, 1958. Density-gradient ultracentrifugation of density- labeled DNA. Figure 20.1
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Getting Started: 1. DnaA protein binds to short sequence motifs at OriC (DnaA boxes). 2. HU protein binds and induces a bend in the DNA that destabilizes the
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GDCB 511 5_1_09 REVIEW _Exam 4 %26 Final(2nd part)_YANG -...

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