finals - translation Flashcards
(T/F) the protein levels in the cell is determined from the rate of initiation of translation phase
true
____ the result when an incorrect reading frame is selected or the wrong amino acids are incorporated into growing polypeptide chain
nonfunctional protein or premature termination
____ the first codon translated in mRNAs
AUG codon
____ the aa encoded by the AUG codon
methionine
(T/F) in both eukaryotes and bacteria, the initiator tRNA is associated with methionine
false
applies to eukaryotes only
____ the modified methionine associated with initiator tRNA in bacteria
N- formylmethionine (fmet)
_____ A special tRNA used at initiation and contains anticodon 3’-UAC-5’ to pair with 5’-AUG-3’
initiator tRNA
(T/F) Initiator tRNAs differ in nucleotide sequence from normal methionine tRNAs
true
(T/F) all proteins are synthesized with methionine (or fmet in bacteria) at the C- terminus
false
at the N-terminus
which of the ff is not true about initiator tRNAs in E. coli?
a. can be tRNA(met) or tRNA(fmet)
b. both tRNAs pair with initiator AUG codon
c. only tRNA(fmet) is formylated
d. tRNA(met) is an unmodified methionine
B
fmet = initiator AUG codon met = internal AUG codon
which of the ff is false?
a. the first step in translation initiation in E.coli is the formation of the 70S initiation complex
b. IF-2 binds GTP and helps to specifically select tRNA(fmet)
c. IF-3 facilitates binding mRNA to 30S subunit and prevents association of 50S subunit
d. the 30S initiation complex includes mRNA, 30S ribosomal subunit, fmet-tRNA(fmet) , GTP, and threeinitiation factors
A
formation of 30S initiation complex
_____ a consensus sequence that functions as a ribosome binding site located about 10 nucleotides upstream from
AUG start codon
Shine-Dalgarno sequence
(T/F) the Shine-Dalgarno sequence is pyrimidine rich
false
purine rich
_____ the Shine-Dalgarno sequence
5’-GGAGGU-3’
(T/F) the S-D sequence is bound by a complementary pyrimidine-rich sequence on the 16S rRNA in the 30S subunit, which functions to align ribosome with initiation AUG codon
true
(T/F) bacterial mRNAs have ribosome binding sites at multiple areas in the mRNA that orients the ribosomes for initiation of translation
true
_____ and ____ are elongation factors that are required for the addition of a new aminoacyl-tRNA to A site of the ribosome
temperature-unstable (EF-TU) and temperature-stable (EF-T) elongation factors
which of the ff is not true?
a. EF-TUguides incoming aminoacyl-tRNAs into P site and facilitates pairing between anticodon and codon
b. EF-TU is the most abundant protein in E. coli
c. EF-Ts functions in regeneration of EF-TU-GTP
d. EF-TU ensures translational fidelity
A
guides tRNAs into the A site
___ the enzyme that catalyzes peptide bond formation between amino acid
peptidyl transferase
______ a process that occurs when uncharged tRNA moves from P site to E site, peptidyltRNA in A site shifts to empty P site, and mRNA moves such that a new codon is accessible at A site
translocation
(T/F) translocation of tRNA in the ribosome requires Elongation factor, EF-G and ATP
false
requires GTP
(T/F) conformational change of EF-G upon GTP hydrolysis that helps to move the tRNA in A site to P site and advance mRNA by one triplet
true
which of the ff is false about peptidyl transferase?
a. it is a component of 50S ribosomal subunit
b. its activity is mediated by catalytic mRNA
c. peptide bond forms between aa in A site and P site
d. its enzyme activity makes ribosomes large ribozymes
B
by catalytic rRNA
(T/F) the structural core of ribosomes is composed of protein that functions to stabilize the structure
false
is composed of rRNA at its core!
(T/F) Protein synthesis is terminated when a stop signal codon reaches the A site
true
which of the ff is NOT a stop codon?
a. UAA
b. UAG
c. UGA
d. UGG
D
(T/F) stop codons are recognized and bound by tRNAs
false
_____ are factors that recognizes a stop codon and functions in the termination of translation
release factors
RF-1, RF-2 and RF-3 in bacteria
which of the ff does not apply to release factors?
a. blocks access by any other aminoacyl tRNAs
b. recognizes stop codons
c. causes peptidyl transferase to catalyze addition of a methyl cap at the end of polypeptide chain
d. its structure resembles tRNA
C
addition of WATER
(T/F) the addition of water to the polypeptide chain leads to its release including the tRNA, mRNA and separation of ribosomal subunits
true
(T/F) translation in eukaryotes are more complex but their initiation phase is similar to that of prokaryotes
false
this is the most significant difference!
(T/F) in eukaryotes, a special met initiator tRNA binds to the 40S subunit through its association with eIF2 and GTP
true
(T/F) in eukaryotes, the Shine-Dalgarno sequence orients the ribosomal binding to the initiator AUG codon
false
no S-D sequence, 5’ cap orients initiation complex instead
_____ the structure that recognizes the complex of cap-associated proteins at 5’ end of mRNA and scans for initiator AUG
43S initiation complex
____ the sequence that distinguishes the initiator AUG from other AUG codons
Kozak consensus sequence (-3ACCAUGG+4)
(T/F) in eukaryotes, a complex of initiation factors associated with 5’ cap orients 43S initiation complex to initiator AUG
true
which of the ff is false?
a. polypeptide elongation in eukaryotes is very similar to that in prokaryotes
b. peptidyl transferase activity is also similar between eukaryotes and prokaryotes
c. eukaryotes and prokaryotes utilize the same three stop codons
d. Eukaryotes have three termination release factor that recognizes all three
stop codons
D
Eukaryotes have 1 only
prokaryotes have 3
_____ a complex in bacteria that forms when one mRNA molecule is associated with multiple ribosomes, speeding up protein synthesis
polyribosome (or polysome)
which of the ff is not true about eukaryotic polysomes?
a. Polyribosomes are found in the nucleus
b. are spaced about 80 nucleotides apart on a single mRNA
c. speeds up synthesis
d. ribosome subunits can be recycled for another round of synthesis
A
found in cytosol
which of the ff is not true?
a. polysomes can be bound to the endoplasmic reticulum to form rough ER
b. both free and ER bound polyribosomes use same pool of ribosomal subunits
c. proteins produced by free polyribosomes can be transported to other parts of the cell
d. Proteins produced in ER are destined for secretion from cell or incorporated into other organelles or plasma membrane
C
they remain in the cytosol
which of the ff about the use of energy by the cell is false?
a. transcription is the most energy demanding process in the cell
b. multiple high energy phosphate bonds from ATP or GTP are utilized
c. extra energy is spent when “proofreading”
d. extra energy is spent when wrong tRNA enters A site of a ribosome and triggers GTP hydrolysis
A
its translation not transcription
____ a special RNA in bacteria that adds an 11 amino acid tag to C-terminus of incomplete protein that targets entire hybrid protein for degradation by proteases
transfer-messenger RNA (tmRNA)
which of the ff about post-translational events is not true?
a. mature proteins undergo some type of post translational modification
b. mature protein production ends at translation
c. mature proteins need to associate with other protein subunits or small cofactors
d. misfolded mature proteins must be degraded
B
must be folded, modified etc
(T/F) Nascent proteins begin to fold while still attached to ribosome and is completed by the time it is released
true
_____ a class of proteins that assists the folding of many proteins while they are being synthesized
molecular chaperones
(T/F) molecular chaperones undergo conformational changes using hydrolysis of GTP to help
shape their target protein
false
uses ATP. the rest is true
_____ is a type of molecular chaperone that provides conducive environment for folding and prevents aggregation of proteins through interactions between misfolded regions that have exposed hydrophobic residues; are barrel-shaped
chaperonin
(T/F) about 30% of of all newly synthesized proteins are rapidly degraded due to errors during transcription, translation, posttranslational modifications, misfolding or other defects
true
(T/F) Proteins destined for degradation are generally targeted to lysosomes or macromolecular structures called proteasomes
true
(T/F) in constructing a genomic DNA library, the otal human DNA is cut into millions of fragments with restriction exonucleases
false
uses ENDOnucleases
____ the entire set of plasmids with all pieces of human DNA
genomic library
_____ are colonies of bacteria containing the same plasmid bearing one human DNA fragment
genomic clones
(T/F) construction of a human genomic library involves, restriction endonucleases, recombinant DNA and transformation
true
____ the chaotrope used to denature cell proteins by disrupting hydrogen bonds and hydrophobic interactions for isolation of RNA from cultured cells
guanidinium thiocyanate
____ used to remove/ extract proteins from the aqueous phase for isolation of total RNA in cultured cells
phenol/chloroform (organic phase)
____ used to precipitate out RNA in aqueous phase in the isolation of total RNA in cultured cells
isopropanol
_____ used to isolate denaturated RNA (in high salt solution)
oligo dT cellulose affinity chromatography column
which of the ff does not apply to isolation of polyadenylated RNA?
a. column is washed to remove unbound RNA
b. poly A+ RNA is eluted with high salt buffer
c. heating RNA removes intramolecular base
pairing
d. uses oligo dT which consists of single stranded molecules of T residues bound to a matrix
B
eluted in LOW salt concentration
______ a complementary DNA that is formed from an mRNA template through the action of the enzyme reverse transcriptase
cDNA
____ an enzyme of retroviruses that can use RNA as a template to synthesize DNA
Reverse transcriptase
which of the ff does not apply to the preparation of cDNA?
a. Reverse transcriptase reaction is primed with an oligo dT primer
b. RNAse H degrades RNA in RNA/DNA duplexes
c. DNA polymerase forms complementary DNA strand to produce a single-stranded cDNA
d. cDNA consist of only exon regions and 5’and 3’
untranslated regions of the mRNA
C
produces DOUBLE stranded cDNA
_____ a special type of plasmid that contains a promoter upstream from inserted cDNA that drives transcription of cDNA once it is introduced into a cell
an expression vector
____ method that uses DNA or gene chips that help indicate gene expression using cDNA probes
microarray
(T/F) multiple ribosome binding sites in the mRNA allows for synthesis of one type of protein in large numbers from one mRNA
false
multiple sites allow synthesis of more than one type of protein from a single mRNA
_____ primer used for construction of cDNA
oligo dT primer
primed w/ reverse transcriptase
_____ degrades in RNA/DNA duplexes
RNAse H
