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39 Cards in this Set
- Front
- Back
What translation sequence is on the mRNA vs tRNA?
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mRNA = codon sequence; tRNA = anti-codon sequence
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What are the start codons?
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AUG(RNA) aka ATG in DNA = methionine
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What are the 3 stop codons?
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1. UAG, 2. UGA, 3. UAA
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What is the wobble hypothesis?
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The fact that there is inosine in the anit-codons means it can fit multiple bases at the 3rd position thus there is less need for unique tRNAs
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What are the rules to the genetic code?
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1. Code is universal, 2. code is non-overlapping, 3. code is degenerate and unambigouous (multiple codons for each AA but only one AA per codon)
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What are the 4 types of mutations?
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1. Point mutations, 2. insertion (extra bases added -> frame shift), 3. deletion (loss of base -> frame shift) , 4. frame shift (occurs in non multiple of 3 deletions/insertion)
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What are the 3 types of point mutations?
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1. Silent (no change in AA), 2. missense (one AA -> a different AA), 3. non-sense (becomes STOP codon -> truncated protein)
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What are the characteristics of splice site mutations?
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1. ↓ splicing efficiency, 2. alters splicing/insertion sequence from intron into mRNA/exon skipping/loss of exon
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What is a triplet repeat expansion?
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Proteins w/long runs of same codon can ↑ over time -> repeats interfere w/protein function/production
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What is the function of aminoacyl-tRNA synthetase
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Transfers AA to growing peptide chain
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Where on the tRNA does the AA attach?
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AA attaches to the terminal adenine of CCA
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Where is the carboxyl group of tRNA on AA attached to?
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Carboxyl group on AA is joined to 3' carbon of adenine by ester bond
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What is the first AA added to each protein?
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Methionine
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What are the steps of translation?
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1. Start chain w/methionine, 2. charged tRNA aligned on mRNA by ribosome, 3. AA transferred from tRNA to growing peptide chain, 4. uncharged tRNA exits and can be attached to AA + used again
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What is the ribosomal binding site in prokaryotes called? Eukaryotes?
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Utilizing 30s/40s; Prokaryotes = shine-dalgarno, eukaryotes = 5' cap and cap binding protein
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In which type of cell is methionine formylated?
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In prokaryotes only
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What is the ribosomal subunit that Met-tRNA binds to?
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50s/60s
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What is the energy source of translation?
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ATP + GTP
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When does a tRNA go directly into the P site of ribosome?
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Initiation only. Elongation = tRNA enters the Asite
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What are the prokaryote initiation factors?
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1. IF-1, 2. IF-2, 3. IF3
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What are the eukaryote initiation factors?
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eIFs
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What are the elongation factors in translation?
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1. EF-Tu(eEF1a), 2. EF-T(eEF-1bg), 3. GTP
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What catalyzes the peptide bond formation?
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Peptidyl transferase (it’s a ribozyme) - 50s or 60s
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What are the requirements for translocation during transcription?
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1. EF-G (eEF2), 2. GTP
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What is the procedure for protein synthesis?
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1. Initiation(assemble translation machinery), 2. elongation (AA added to carboxyl end of growing chain), 3 translocation(movement of ribosome along mRNA); 4.. termination(looks for STOP codon -> release factors bind -> peptidyl transferase hydrolyzes bond between polypeptide and final tRNA)
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What are the requirements for termination in transcription?
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STOP codons (1. UAG, 2. UGA, 3. UAA)
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How do u get faster overall translation?
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Have multiple ribosomes attach to the same mRNA -> as a ribosome translocates away from 5' end another is recruited
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What is unique about prokaryotes first AA?
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The Initial methionine does not have a Free amino group-> insead fMet tRNA(formyl transferase enzyme adds formy group(which looks like a peptide bond)) -> then removed later
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Define: post-translational modification
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Proteins can be modified after synthesis -> add groups/modify function/activity/help target protein to sub-cellular compartments
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Which AA does carboxylation occur?
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Carboxylation of Glutamine (ie coagulation cascade)
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Which AA does hydroxylation occur?
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Hydroxylation of Proline + lysine(ie collagen stability)
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Which AA does phosphorylation occur?
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Phosphorylation of Serine, Threonine, Tyrosine(ie enzyme activity)
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Which AA does Glycosylation occur?
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Glycosylation of serine + asparagine (ie secretion, membrane)
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What is the protein that is used to recognize new proteins in the rER?
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Signal recognition particle (SRP) - used to dock w/receptor on ER -> new peptide is threaded thru this pore -> modified protein -> enters secretion pathway
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What is the tag that is added to lysosomes in the Golgi?
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Mannose-6-phosphate; thus deficiency = i-cell disease where the lysosomes are not kept inside the cell b/c it doesn't know where to go and is sent outside the cell
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Function of streptoycin
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Binds to 16S rRNA of 30s subunit -> inhibits translation initiation
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Function of tetracycline
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Binds to 30S ribosome subunit -> blocks binding of aminoacyl-tRNA to the A site of ribosome
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Function of chloramphenicol
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Binds 50S ribosomal subunits -> blocks bindings of AA on aminoacyl-tRNA -> blocks peptidyltransferase activity -> inhibit mitochondrial activity -> only used under serious conditionss
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Function of erythromycin
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Binds to 50S ribosomal subunits -> prevents translocation (movement of tRNA from A -> P site)
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