Unit9-1STUDENTS - 1. Eukaryotic RNAs are modified before...

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Unformatted text preview: 1. Eukaryotic RNAs are modified before export to cytoplasm 2. Prokaryotic RNAs are not modified 3. 5 cap addition of a G residue in a 5 5 linkage followed by methylation of G and 2 methylation of 1 st 1-2 nucleotides of transcript 4. Polyadenylation involves cleavage of the RNA between 2 recognition motifs, followed by addition of A residues by polyA polymerase 5. Role of cap and poly(A) tail 6. PolyA tail and cap act synergistically to increase translation Review of Unit 8 Review of Unit 8 (cont) 1. Splicing removal of introns from pre-mRNA 1. Consensus sequences for splicing Sequences in intron ( GU----- AG ) Branch point consensus Sequences in exon 1. Lariat model of splicing Today-Complete Unit 8 1. Spliceosome protein and snRNAs that base pair with splice junctions and branch point 2. Spliceosome cycle includes the assembly, splicing activity and dissassembly of the spliceosome Unit 9: Translation Reading: Weaver pp. 31-36, 41-46, 521-638 Outline for Unit 9 1. Experiments to determine the genetic code 2. Amino acid structure 3. Components of translation tRNA ribosomes mRNA other factors 1. Protein structure 2. Overview of translation 3. tRNA structure synthesis charging 7. Ribosome structure DNA RNA Protein Protein synthesis (translation) RNA synthesis (transcription) DNA replication CENTRAL DOGMA Coding strand Coding strand Deciphering the Genetic Code 1. The code is a triplet code 2. The code is degenerate (>1 codon per aa) 4. The 3rd base is often flexible (WOBBLE ) 1. Some codons encode " stop 2. No gaps or overlaps between codons 6. The code is almost universal The Genetic Code The Genetic Code No gaps or overlaps between codons W/commas W/Ocommas AUG Z CAG Z CCA Z ACG Z AUG CAG CCA ACG Effect of inserting one nucleotide AU X G Z CAG Z CCA Z ACG Z AU X GCA GCC AAC G Frameshift mutation Late 1950's- unstable RNA identified that bound ribosomes (mRNA)- amino acids shown to complex with small RNAs on ribosomes (tRNA) Early 1960s- deciphering of genetic code R. W. Holley, H. G. Khorana, and M. W. Nirenberg received the Nobel Prize in 1968 "Interpretation of the genetic code and its function in protein synthesis" History of the genetic code Deciphering The Genetic Code Several approaches were used: 1. In vitro protein synthesis using synthetic mRNA 2. Oligonucleotide binding assays 3. Nonsense/suppressor mutations Deciphering The Genetic Code...
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Unit9-1STUDENTS - 1. Eukaryotic RNAs are modified before...

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