341lecture11oct2sakai

341lecture11oct2sakai - Cell Biology 341 Last lecture:...

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Cell Biology 341 Friday, October 2, 2009 Today: Alternative splicing translation of mRNA on ribosomes See videos 6.1 through 6.10, and 3.10, on your DVD Bring two #2 pencils to the exam next Friday, Oct 9 Office hours next week: Tues 10-noon, Thurs 2-4 pm Last lecture: Processing of eucaryotic primary transcripts: a 7-methyl-G “cap”, linked 5'-5', is added to the 5'-end Introns are removed by the spliceosome in two transesterification reactions that generate a lariat structure A poly-A tail is added to the 3'-end after cleavage between two conserved sequences
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Introns may have facilitated the evolution of eucaryotic genes by recombination of domains to generate new proteins Many eucaryotic genes undergo alternative splicing to produce different mRNAs, and thus different polypeptides, from the primary transcript of a single gene Figure 6-27 Regulates muscle contraction Polyadenylation sites
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How can an alphabet of 4 nucleotides specify 20 amino acids? Two nucleotides per amino acid: 4 2 = 16 (not enough) 3 nucleotides per amino acid: 4 3 = 64 (more than enough) One codon of 3 nucleotides specifies one amino acid There are extra codons for some amino acids; variation occurs in the third position The genetic code is universal among procaryotes and eucaryotes (except for mitochondrial DNA) Figure 6-50 stop Initiation codon (start)
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tRNA delivers the correct amino acid to the ribosome during protein synthesis Internal base-pairing (secondary structure) causes tRNA to fold into a helical L-shape Anticodon base-pairs with codon of mRNA Amino acid
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This note was uploaded on 12/05/2009 for the course BIO 341 taught by Professor Noris during the Fall '09 term at Rhode Island.

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341lecture11oct2sakai - Cell Biology 341 Last lecture:...

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