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39 Cards in this Set

  • Front
  • Back
What translation sequence is on the mRNA vs tRNA?
mRNA = codon sequence; tRNA = anti-codon sequence
What are the start codons?
AUG(RNA) aka ATG in DNA = methionine
What are the 3 stop codons?
1. UAG, 2. UGA, 3. UAA
What is the wobble hypothesis?
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
What are the rules to the genetic code?
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)
What are the 4 types of mutations?
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)
What are the 3 types of point mutations?
1. Silent (no change in AA), 2. missense (one AA -> a different AA), 3. non-sense (becomes STOP codon -> truncated protein)
What are the characteristics of splice site mutations?
1. ↓ splicing efficiency, 2. alters splicing/insertion sequence from intron into mRNA/exon skipping/loss of exon
What is a triplet repeat expansion?
Proteins w/long runs of same codon can ↑ over time -> repeats interfere w/protein function/production
What is the function of aminoacyl-tRNA synthetase
Transfers AA to growing peptide chain
Where on the tRNA does the AA attach?
AA attaches to the terminal adenine of CCA
Where is the carboxyl group of tRNA on AA attached to?
Carboxyl group on AA is joined to 3' carbon of adenine by ester bond
What is the first AA added to each protein?
Methionine
What are the steps of translation?
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
What is the ribosomal binding site in prokaryotes called? Eukaryotes?
Utilizing 30s/40s; Prokaryotes = shine-dalgarno, eukaryotes = 5' cap and cap binding protein
In which type of cell is methionine formylated?
In prokaryotes only
What is the ribosomal subunit that Met-tRNA binds to?
50s/60s
What is the energy source of translation?
ATP + GTP
When does a tRNA go directly into the P site of ribosome?
Initiation only. Elongation = tRNA enters the Asite
What are the prokaryote initiation factors?
1. IF-1, 2. IF-2, 3. IF3
What are the eukaryote initiation factors?
eIFs
What are the elongation factors in translation?
1. EF-Tu(eEF1a), 2. EF-T(eEF-1bg), 3. GTP
What catalyzes the peptide bond formation?
Peptidyl transferase (it’s a ribozyme) - 50s or 60s
What are the requirements for translocation during transcription?
1. EF-G (eEF2), 2. GTP
What is the procedure for protein synthesis?
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)
What are the requirements for termination in transcription?
STOP codons (1. UAG, 2. UGA, 3. UAA)
How do u get faster overall translation?
Have multiple ribosomes attach to the same mRNA -> as a ribosome translocates away from 5' end another is recruited
What is unique about prokaryotes first AA?
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
Define: post-translational modification
Proteins can be modified after synthesis -> add groups/modify function/activity/help target protein to sub-cellular compartments
Which AA does carboxylation occur?
Carboxylation of Glutamine (ie coagulation cascade)
Which AA does hydroxylation occur?
Hydroxylation of Proline + lysine(ie collagen stability)
Which AA does phosphorylation occur?
Phosphorylation of Serine, Threonine, Tyrosine(ie enzyme activity)
Which AA does Glycosylation occur?
Glycosylation of serine + asparagine (ie secretion, membrane)
What is the protein that is used to recognize new proteins in the rER?
Signal recognition particle (SRP) - used to dock w/receptor on ER -> new peptide is threaded thru this pore -> modified protein -> enters secretion pathway
What is the tag that is added to lysosomes in the Golgi?
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
Function of streptoycin
Binds to 16S rRNA of 30s subunit -> inhibits translation initiation
Function of tetracycline
Binds to 30S ribosome subunit -> blocks binding of aminoacyl-tRNA to the A site of ribosome
Function of chloramphenicol
Binds 50S ribosomal subunits -> blocks bindings of AA on aminoacyl-tRNA -> blocks peptidyltransferase activity -> inhibit mitochondrial activity -> only used under serious conditionss
Function of erythromycin
Binds to 50S ribosomal subunits -> prevents translocation (movement of tRNA from A -> P site)