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Molecular test #5

Terms in this set (26)

IF3
Keeps ribosomal subunits from reassociating
fMET-tRNA
The initiator tRNA in prokaryotes
EF-tu
Has GTPase activity during translation elongation
Met- tRNA
The initiator tRNA in eukaryotes
IF1
causes disassociation of ribosomal subunits
Puromycin
Causes premature termination of translation
60S subunit
Contains peptidyl transferase activity in eukaryotes
GDPCP
unhydrolyzable analogue of GTP
CCRCCAUGG
The kozak sequence
AGGAGGU
The shine-dalgarno sequence
If a mi-RNA has a perfect complimentary match to an existing mRNA, then which outcome below would be expected to occur?
The mRNA would be degraded prior to translation
GTP binding is required for IF2 to bind to fMET-tRNA and the small ribosomal subunit in prokaryotes
True
Prokaryotes use three initiation factors in the construction of the translational initiation complex
True
The ribosome is incapable of proofreading the amino acid brought in by the incoming charged tRNA molecule
True
Translocation of the ribosome to the next available codon requries
both a and b (GTP and EF-G)
The 3-dimensional structure of a tRNA most resembles
a capital L
tRNAs often undergo post-transcriptional chemical modification of their nucleotides
True
One important first step in the translation of eukaryotic mRNA is the unwinding of the transcript at the 5' end
True
The genetic code that is used in all species actually does seem to have a selective advantage, which is
The code is remarkably non-susceptible to error
You have 2 samples of mRNA, both with 5' caps, but to one sample you add Cap-binding protein and to the other you do not. Both mixes are added to separate cell-free extracts containing 35S-labeled methionine. What would you expect to see as the outcome in terms of 35S incorporation into polypeptides? (mult. choice)
The amount of incorporation would be greater in the sample with Cap-binding protein because cap-binding protein stimulates translation
What is the scanning model of translation in eukaryotes?
The 40S? ribosomal subunit starts at the 5'cap in mRNA and starts scanning until it reaches the first start AUG that looks good enough to be a start codon. The 60s ribosomal unit comes and binds and then translation begins.
EF-G has been found to be required in the process of translation termination. What role does EF-G play in this process?
EF-G plays and important role in translocation. This seems to be an important factor in termination because when you translocate the whole ribosomal unit destabilizes and falls apart.
In what way does the wobble hypothesis of the genetic code differ from the super-wobble hypothesis?
The wobble hypothesis is very important in the genetic code because it allows for the third base wobble which makes it possible to have different third bases in the sequence that code for the same amino acid. The super-wobble hypothesis is like the wobble hypothesis but even more exaggerated with the bases being able to pair more loosely.
Why was titrated fMet used as the label?
Because fMet will be the --- tRNA incorporated into the ribosome so you will be able to see the pmol released because the fMet will always be at the beginning of the amino chain. You will be able to see it when it releases.
Do the release factors show differential recognition of the stop codons? support
Yes, RF1 requires UAA and UAG. RF2 recognizes UAA and UGA. There are higher concentrations of each by their certain factor.
Do the release factors show differential activity at different Mg2+ concentration? support
Yes, there is more pmol? fMet released with .030m mg2+ than with .012m mg2+. For both release factors this is true because both of the concentrations increase when .030 mg2+ is present.
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