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