Translation Flashcards
What is the central dogma of molecular biology?
DNA replicates into DNA
DNA is transcribed into RNA
RNA is translated into proteins
What is the genetic code?
Ribonucleotide language on mRNA
What is the role of tRNA?
Interprets mRNA code in AA by its anticodon loop
What are the three stop codons?
UAA
UGA
UAG
What is the start codon and what does it code for?
AUG
Methionine
What are the four properties of the genetic code?
Universal
Unambiguous
Degenerate/redundant
Non-overlapping and continuous
What is the open reading frame?
Genetic code from start codon to stop codon
What are the 5 mutations in nucleotide sequence?
Base substitution/point mutations
Frame shift mutations
Splice site mutations
Trinucleotide repeat expansion
Large segment deletion
What are the three point mutations?
Silent
Missense
Nonsense
What is a silent mutation?
Same AA
What is a missense mutation?
Different AA
What is a nonsense mutation?
Premature stop codon
What is a frame shift mutation?
Deletion or insertion of 1-2 nucleotides
OR
Deletion of insertion of 3 nucleotides
What are the requirements of translation?
mRNA
AAs
tRNA
Ribosomes
Translation factors
Energy
How does AA attach to tRNA?
Attaches to CCA at 3’ end
What is the wobble hypothesis?
Many tRNAs can pair to same codon as last nucleotide of codon (first in tRNA) is in a wobble position
What is the function of the small subunit of ribosomes?
Binds to mRNA
Correct base-pairing between codon and anticodon
What is the function of the large ribosomal subunit?
Catalytic peptidyl transferase activity of 23S rRNA in prokaryotes and 28s in eukaryotes - peptide bond formation
What are the three binding sites for tRNA and their functions?
A - accepts new tRNA and matches to codon
P - formation of peptide bonds
E - exit site
What are the translation factors?
Initiation factors (IFs)
Elongation factors (EFs)
Termination Factors (RFs)
What is used for energy in translation?
GTP
ATP
What are the 4 steps of translation?
Preinitiation
Initiation
Elongation
Termination
What does polycistronic mean?
Multiple coding regions on one mRNA seen in prokaryotes
What does monocistronic mean?
One coding region on mRNA - only option in eukaryotes
What is pre-initiation and its energy requirements?
Activation of AA - aminoacylated tRNA
Two high energy bonds from ATP
What is initiation?
mRNA and met-tRNA bind to ribosome
Formyl added to met-tRNA in prokaryotes at start codon only
What is elongation in translation?
Successive cycles of active tRNA binding and peptide bond formation until stop codon is reached
What is termination?
Once stop codon is reached, mRNA and tRNA dissociate, ribosome subunits are recycled
What is the Shine-Dalgarno sequence?
Initiation site in prokaryotes upstream of start codon that binds to 16S rRNA of small subunit
Is then bound with IFs
How many and what type of energy bonds are required for translation in prokaryotes?
2 ATP
2 GTP
+1 GTP for termination
Extra needed in eukaryotes
Where to the products go from translation on free ribosomes?
Nucleus
Mitochondria
Peroxisomes
Stay in cytosol
Where to the products go from translation on rER?
Exported from cell
Plasma membrane
Lysosomes
What is the signal for translation in eukaryotes?
Kozak sequence - ACCAUGG
What is the function of eIF4?
Binds to the 5’ cap of mRNA which allows preinitiation complex to bind forming initiation complex
How are proteins folded?
By chaperones, concurrent with translation
Misfolded proteins are either refolded are degraded
What is the function of protein targeting and how does it work?
Specific AA sequences direct proteins
Secretory or non-secretory paths to destinations
What is added to proteins destined for lysosome?
M6P
What are some inhibitors of prokaryotic protein synthesis?
Streptomycin
Neomycin
Puromycin
Chloramphenicol
Erythromycin
What are some inhibitors of eukaryotic protein synthesis?
Diphtheria toxin
Pseudomonas
Ricin
Cycloheximide
Shiga and shiga-like toxin
