BIO 230 EXAM #2 QUESTIONS AND
ANSWERS
What is alternative RNA splicing and is it bad? - ANSWER-can result in multiple
proteins synthesized from one mRNA---common not always bad but can be bad
when it isn't regulated
In alternative RNA splicing---additional regulatory proteins exist that can do what? -
ANSWER-inhibit or enhance splicesome formation---bind to conserved regions and
"mask" them from the snRNP recognition (exon skipping)
video: https://www.youtube.com/watch?v=FAsLzgVHmjQ
when the mRNA is matured where is transported? - ANSWER-out of the nucleus and
are translated by ribosomes either in the cytoplasm or in the ER
Proteins destined for export are translated into what via what? - ANSWER-ER lumen
via translocon protein complex
where does translation begin? where does it finish? what is the final product and
then what happens to the new protein? - ANSWER-in the cytoplasm--- finishes into
the ER---signal peptide(mRNA has a code that makes this) part of the new protein---
the new protein then can be packaged in the vesicle for transport
if the mRNA codes for a signal peptide as part of the new protein...what does the
signal recognition particle (SRP) do? - ANSWER-binds to the translated signal
peptide and facilitates binding of the ribosome to a translocon
What is anterograde transport after translation? - ANSWER-typical normal
movement of a protein---describes the path of a newly synthesized protein destined
for export---DNA->mRNA(pre-mRNA)
which of the following correctly describes the order of organelles involved in export?
- ANSWER-ER--->vesicle--->golgi--->vesicle--->plasma membrane
What is a ribosome composed of? - ANSWER-ribonucleoprotein that is composed of
rRNA and proteins and ribozyme activity(rna molecule that can catalyze a reaction-
peptide bond formation)
large subunit binds to? small subunit binds to? E,P,A sites are? - ANSWER-binds to
tRNA----binds to mRNA---movement of tRNAs through the large ribosome subunit
E,P,A sites - ANSWER-movement of tRNAs through the large ribosome subunit---E
site= exit site, P site=peptidyl-tRNA binding site, A site=aminoacyl-tRNA binding site
activators in the pre-initiation complex - ANSWER-promote stabilization-->promote
complex formation--> increase in mRNA production
,repressors in the pre-inititiation complex - ANSWER-inhibit stabilization--> inhibit
complex formation--> reduce mRNA production
When turning off transcription what does it favor? - ANSWER-make favouring
nuclesome formation makes it more heterochromatic
what is the teeter-totter analogy? - ANSWER-there is a basal rate of
transcription/minute (if basal TFs are present then activators and repressors will alter
this rate)
Transcription termination in eukaryotes is related to? - ANSWER-polyadenylation
signal
What helps position proteins involved in the Poly-A tail to transcription termination? -
ANSWER-PolyA-signal and PolyA-site
After the termination of transcription what happens to RNA polymerase? - ANSWER-
it dissociates from the DNA template after these sequences are transcribed
Where do the steps of pre-mRNA processing occur? - ANSWER-in the nucleus---
transcription before we leave must have mRNA fully processed
Where do the steps of translation occur? - ANSWER-cytoplasm
steps involved in the eukaryotic pre-mRNA processing-- what are the start and stop
codons - ANSWER-start=AUG, stop=UAG---5' cap(guanine modified w/ a methyl
group) added to protect mRNA from degeneration and promote nuclear export---
splicesome (snRNA and snRNPs in the nucleus) removes introns---3' Poly-A tail is
added to help protect mRNA from degradation and promote nuclear export----final
result is mature mRNA
which of the following is true regarding snRNPs? - ANSWER-they contain RNA and
protein---form formation of splicesomes---(small nuclear ribonucleoproteins)
what does role do the RNA and protein play in the snRNP? - ANSWER-RNA
component binds to conserved regions on introns (specificity)--helos the splice some
specifically find introns
Protein components facilitate excision of the introns
The splicing process is----what causes the intron to "bend"? what then causes more
bending and what else does it facilitate? - ANSWER-RNA component binds to intron
based on conserved sequences in the introns---interactions btw snRNPs and
additional proteins---conformational changes to the protein causes more bending
and facilitates intron splicing via a chemical rxn.
during transcription, mutations are introduced into the conserved regions of two
introns. If these mutations prevent snRNP recognition, which protein will be result
after translation? - ANSWER-removes the exons because the splicesome thinks they
are introns
, what is transfer RNA? what does it contain? "charged" tRNA? - ANSWER-they add
a.a to RNA-single strand of RNA that has a secondary structure mediated by
hydrogen bonds---anticodon region and a.a binding region---a.a. bound completed
by aminoacyl tRNA synthase
the tRNAs anticodon binds to what at what site? the genetic code is redundant or
degenerate what is this process called? - ANSWER-to the mRNA codons synthesize
the protein at the A site....multiple codons for one amino acid called the wobble effect
the wobble occurs where? - ANSWER-at the third position of the codon
what are the 2 main mechanisms for the wobble effect? - ANSWER-1.) non-
canonical binding at third positions due to less steric hindrance so instead of G-C in
third position it is G-U---variability is happening in the 3rd position-> less of a shape
confinement for it to match
2.) anticodon can contain the base inosine (related to adenine) that binds to U, C, or
A(post transcriptional modification pairs w/ everything)
What three major steps does translation involve? - ANSWER-initiation, elongation,
termination
initiation contains- - ANSWER-start codon, initiation factors, 5' mRNA cap, GTP
hydrolysis, small/large ribosomal subunits
GTP hydrolysis - ANSWER-couple reactions to occur that may not normally occur
Elongation contains- - ANSWER-EF-Tu, EF-G-> bacteria (prokaryote), ribozyme,
peptidyltransferase, A site, P-site, translocate, GTP hydrolysis
Termination contains- - ANSWER-stop codon, release factor, GTP hydrolysis
Explain initiation? - ANSWER-small ribosomal subunit associates to 5' cap for
mRNA---requires initiation factors(proteins) and tRNA-Methionine--initiation factors
hydrolyze GTP to provide energy to form the ribosome and initiation factors are
released, large subunit binds
EFs utilize GTP to facilitate accurate what? - ANSWER-translation and translocation
of mRNA
Translation steps- - ANSWER-1.) EF-1 (Tu) helps correct tRNA to enter the A site---
GTp hydrolyzes w/ correct pairing because of stabilized codon anticodon interactions
2.) Ribozyme peptidyltransferase activity synthesizes a new peptide bond to the
amino acid in the A site
3.)EF-2 (G) translocates tRNA from P->E only empty tRNA---occurs after the peptide
bond formation and frees the A-site for the next tRNA
what happens during termination? - ANSWER-when a stop codon is encountered---
release factor(protein) bind to codon in the A site= triggers GTP hydrolysis and of the
new peptide chain ---after hydrolysis the ribosome complex dissociates
ANSWERS
What is alternative RNA splicing and is it bad? - ANSWER-can result in multiple
proteins synthesized from one mRNA---common not always bad but can be bad
when it isn't regulated
In alternative RNA splicing---additional regulatory proteins exist that can do what? -
ANSWER-inhibit or enhance splicesome formation---bind to conserved regions and
"mask" them from the snRNP recognition (exon skipping)
video: https://www.youtube.com/watch?v=FAsLzgVHmjQ
when the mRNA is matured where is transported? - ANSWER-out of the nucleus and
are translated by ribosomes either in the cytoplasm or in the ER
Proteins destined for export are translated into what via what? - ANSWER-ER lumen
via translocon protein complex
where does translation begin? where does it finish? what is the final product and
then what happens to the new protein? - ANSWER-in the cytoplasm--- finishes into
the ER---signal peptide(mRNA has a code that makes this) part of the new protein---
the new protein then can be packaged in the vesicle for transport
if the mRNA codes for a signal peptide as part of the new protein...what does the
signal recognition particle (SRP) do? - ANSWER-binds to the translated signal
peptide and facilitates binding of the ribosome to a translocon
What is anterograde transport after translation? - ANSWER-typical normal
movement of a protein---describes the path of a newly synthesized protein destined
for export---DNA->mRNA(pre-mRNA)
which of the following correctly describes the order of organelles involved in export?
- ANSWER-ER--->vesicle--->golgi--->vesicle--->plasma membrane
What is a ribosome composed of? - ANSWER-ribonucleoprotein that is composed of
rRNA and proteins and ribozyme activity(rna molecule that can catalyze a reaction-
peptide bond formation)
large subunit binds to? small subunit binds to? E,P,A sites are? - ANSWER-binds to
tRNA----binds to mRNA---movement of tRNAs through the large ribosome subunit
E,P,A sites - ANSWER-movement of tRNAs through the large ribosome subunit---E
site= exit site, P site=peptidyl-tRNA binding site, A site=aminoacyl-tRNA binding site
activators in the pre-initiation complex - ANSWER-promote stabilization-->promote
complex formation--> increase in mRNA production
,repressors in the pre-inititiation complex - ANSWER-inhibit stabilization--> inhibit
complex formation--> reduce mRNA production
When turning off transcription what does it favor? - ANSWER-make favouring
nuclesome formation makes it more heterochromatic
what is the teeter-totter analogy? - ANSWER-there is a basal rate of
transcription/minute (if basal TFs are present then activators and repressors will alter
this rate)
Transcription termination in eukaryotes is related to? - ANSWER-polyadenylation
signal
What helps position proteins involved in the Poly-A tail to transcription termination? -
ANSWER-PolyA-signal and PolyA-site
After the termination of transcription what happens to RNA polymerase? - ANSWER-
it dissociates from the DNA template after these sequences are transcribed
Where do the steps of pre-mRNA processing occur? - ANSWER-in the nucleus---
transcription before we leave must have mRNA fully processed
Where do the steps of translation occur? - ANSWER-cytoplasm
steps involved in the eukaryotic pre-mRNA processing-- what are the start and stop
codons - ANSWER-start=AUG, stop=UAG---5' cap(guanine modified w/ a methyl
group) added to protect mRNA from degeneration and promote nuclear export---
splicesome (snRNA and snRNPs in the nucleus) removes introns---3' Poly-A tail is
added to help protect mRNA from degradation and promote nuclear export----final
result is mature mRNA
which of the following is true regarding snRNPs? - ANSWER-they contain RNA and
protein---form formation of splicesomes---(small nuclear ribonucleoproteins)
what does role do the RNA and protein play in the snRNP? - ANSWER-RNA
component binds to conserved regions on introns (specificity)--helos the splice some
specifically find introns
Protein components facilitate excision of the introns
The splicing process is----what causes the intron to "bend"? what then causes more
bending and what else does it facilitate? - ANSWER-RNA component binds to intron
based on conserved sequences in the introns---interactions btw snRNPs and
additional proteins---conformational changes to the protein causes more bending
and facilitates intron splicing via a chemical rxn.
during transcription, mutations are introduced into the conserved regions of two
introns. If these mutations prevent snRNP recognition, which protein will be result
after translation? - ANSWER-removes the exons because the splicesome thinks they
are introns
, what is transfer RNA? what does it contain? "charged" tRNA? - ANSWER-they add
a.a to RNA-single strand of RNA that has a secondary structure mediated by
hydrogen bonds---anticodon region and a.a binding region---a.a. bound completed
by aminoacyl tRNA synthase
the tRNAs anticodon binds to what at what site? the genetic code is redundant or
degenerate what is this process called? - ANSWER-to the mRNA codons synthesize
the protein at the A site....multiple codons for one amino acid called the wobble effect
the wobble occurs where? - ANSWER-at the third position of the codon
what are the 2 main mechanisms for the wobble effect? - ANSWER-1.) non-
canonical binding at third positions due to less steric hindrance so instead of G-C in
third position it is G-U---variability is happening in the 3rd position-> less of a shape
confinement for it to match
2.) anticodon can contain the base inosine (related to adenine) that binds to U, C, or
A(post transcriptional modification pairs w/ everything)
What three major steps does translation involve? - ANSWER-initiation, elongation,
termination
initiation contains- - ANSWER-start codon, initiation factors, 5' mRNA cap, GTP
hydrolysis, small/large ribosomal subunits
GTP hydrolysis - ANSWER-couple reactions to occur that may not normally occur
Elongation contains- - ANSWER-EF-Tu, EF-G-> bacteria (prokaryote), ribozyme,
peptidyltransferase, A site, P-site, translocate, GTP hydrolysis
Termination contains- - ANSWER-stop codon, release factor, GTP hydrolysis
Explain initiation? - ANSWER-small ribosomal subunit associates to 5' cap for
mRNA---requires initiation factors(proteins) and tRNA-Methionine--initiation factors
hydrolyze GTP to provide energy to form the ribosome and initiation factors are
released, large subunit binds
EFs utilize GTP to facilitate accurate what? - ANSWER-translation and translocation
of mRNA
Translation steps- - ANSWER-1.) EF-1 (Tu) helps correct tRNA to enter the A site---
GTp hydrolyzes w/ correct pairing because of stabilized codon anticodon interactions
2.) Ribozyme peptidyltransferase activity synthesizes a new peptide bond to the
amino acid in the A site
3.)EF-2 (G) translocates tRNA from P->E only empty tRNA---occurs after the peptide
bond formation and frees the A-site for the next tRNA
what happens during termination? - ANSWER-when a stop codon is encountered---
release factor(protein) bind to codon in the A site= triggers GTP hydrolysis and of the
new peptide chain ---after hydrolysis the ribosome complex dissociates
