6 Translation Flashcards
How is the genetic code described?
degenerate, unambiguous, non overlapping and nearly universal
what are the stop codons
UGA UAA UAG
what is the start codon
AUG
What is the wobble hypothesis
allows for the I anticodon on tRNA to bind U, C and A
what are the different types of mutations
point mutations- base change leads to nonsense, missense or silent results
InDel mutations which can lead to frameshift mutations (can be from splicing)
Inversion mutations which may framshift
triplet expansion - alters proteins, may need to accumulate
how are AA bound to tRNA?
via a specific aa-tRNA synthetase for each type of aa will bind the aa to CCA on 3’ of tRNA by ester bond
how does aa-tRNA synthetase correct errors
the aa-tRNA synthetase have an editing site that can remove aa from tRNA if incorrect
what does a protein chain always start with and why?
proteins start with methionine sine the start codon codes for it, may be changed at final product by post tran mods
what is the general mechanism of ribosomes
met-tRNA binds to P site once AUG is recognized on mRNA, all other aa-tRNA binds on A site and pushes over, tRNA on E site is uncharged so leaves
Where is the start codon usually located in
the kozak concensus sequence
what does the initial tRNA have to bind to initiate?
it must bind to eIF4F which is eIF4A/G/E then bind to large ribosomal subunit on the P site and near the 5’ methyl cap on the mRNA
how any eIF does proks have? euks?
proks 3 eIF
euks >12 eIF
what is the start sequence for proks called?
shine-dalgarno sequence
ribosome reads in which direction?
5’ to 3’
what are the functions of elongation factors?
eEF-Tu/S (eEF-1 on euks) guides tRNA to A site
EF-G(EF-2 on euks) moves tRNA from A to P and P to E sites
Uses up GTP in the process
how is aa added to the protein chain at the P site?
peptidyl transferase RIBOZYME forms a peptide bond from AA to COOH end of protein
how does termination of RNA translation occur
stop codon is reached and release factors and peptidyl transferase hydrolyzes bond on last tRNA and protein
What are polysomes and their reason
multiple ribosomes working on the same mRNA at different areas due to short longevity of mRNA and increased efficiency
what is the difference in initial aa residues in proks and euks?
fMet for proks and Met for euks
how is fMet created?
formyl transferase is used
what does post tran mod do
mods function, activity and targeting of final protein
how are proteins to be secreted synthed?
a signal peptide binds at SRP of newly forming protein which will direct it to rER SRP receptor and protein continues to be synthed into the pore of rER and then have signal peptide cleaved off by signal peptidase
how are proteins targeted for degradation modified?
they have a mannose6p tag
what occurs when phosphotransferases like hexoaminidase A is deficient?
M6P cannot bind and ends up with I(nclusion) cell diseases like tay sachs which leads to accumulating odd proteins
give 4 examples of protein inhibitors and how they work
streptomycin binds 16S rRNA of 30S subunit and blocks initiation
Tetracycline binds 30S and inhibits A site binding (elongation)
Chloramphenicol binds 50S and inhibits peptidyl transferase (elongation) adverse mito
Erythromycin binds 50S prevents A to P translocation
