translation

Question 1

the process of protein synthesis is called ____________, and it occurs on an enzyme complex called the ___________.

Answer 1

translation; ribosome

Question 2

codon

Answer 2

series of three bases specifying one amino acid in a protein; code read 5’->3’ and protein is synthesized from amino- (N-) to the carboxyl- (C-) terminus

Question 3

open reading frame (ORF)

Answer 3

encodes the primary sequence of only one protein
- begins with start codon (AUG) and ends at a stop codon
- ORF is continuous series of codons
- genetic code is non-overlapping

Question 3

the code is degenerate which means

Answer 3

most amino acids are encoded by more than one codon
- leu, arg, ser have 6 codons each
- met and trp only have 1

Question 4

mutation

Answer 4

accidental change in a DNA sequence. it may affect the sequence of a protein encoded in an mRNA

Question 5

nonsense mutation

Answer 5

introduces a stop codon; normally results in a nonfunctional protein

Question 6

missense mutation

Answer 6

replaces one amino acid codon with another; protein effects depend on many things

Question 7

silent mutation

Answer 7

changes the DNA sequence without altering the encoded protein

Question 8

frameshift mutations

Answer 8

caused by an insertion or a deletion within a coding sequence, but the change is not a multiple of 3 bases
- often leads to an early stop codon truncating a protein
- mutations that affect RNA splicing often generate frameshifts

Question 9

what is the most frequent mutation associated with cystic fibrosis?

Answer 9

an in-frame deletion of UUC (phe) codon in CFTR

Question 10

_______ deliver aminos acids to the ribosome
- cloverleaf secondary structure
- many modified bases
- have AAs bound at 3’ end

Answer 10

tRNAs

Question 11

the primary determinants for amino acid selection are _______________________________.
- a tRNA _______ base pairs to a mRNA codon in an antiparallel orientation.

Answer 11

bases #1 and #2 of the mRNA codon; anticodon

Question 12

the third base of many codons pairs loosely, or wobbles, with the corresponding base of its anticodon. this base is known as the ______________

Answer 12

wobble base

Question 13

tRNAs can bind to multiple different codons that encode an amino acid because…

Answer 13

of the leniency at the wobble position
- 32 tRNAs needed to translate all codons

Question 14

non canonical base pairs are allowed at wobble bases (codon #3 to anticodon #1)

Answer 14

anticodon U=A or U=G
anticodon G-=C or G=U
anticodon inosinate (I) I=A or I=U or I=C

Question 15

___________________ read variant sequence elements to select the correct tRNA to be charged with a particular amino acid

Answer 15

aminoacyl-tRNA synthetases

Question 16

the _____________ dictate 3D structure of tRNAs

Answer 16

invariant

Question 17

each amino acid requires its own ___________________

Answer 17

aminoacyl-tRNA synthetase

Question 18

ribosomes are __________ and only ___________ by wieight

Answer 18

65% rRNA; 35% protein

Question 19

prokaryotes have one ribosome, ______________

Answer 19

the 70S ribosome

Question 20

eukaryotic cells have at least two:

Answer 20

80S ribosomes in the cytoplasm and endoplasmic reticulum
mitochondria have a 55S ribosome

Question 21

ribosomes have 3 tRNA binding sites:

Answer 21

A site for aminoacyl tRNA ( where charged tRNA enters)
P site for peptidyl tRNA (attached to growing peptide)
E site for empty (where uncharged tRNA goes to exit)

Question 22

polysomes

Answer 22

multiple ribosomes bound to a single mRNA

Question 23

______________ act on the _____________.
- _______ blocks premature tRNA binding at the A site
-_______ blocks premature binding of the 50S subunit
-mRNA binds to the 30S subunit by base pairing between the 16S rRNA and the Shine-Dalgarno sequence. (as a result, the AUG start codon is arranged into the P-site)

Answer 23

initiation factors; 30S ribosomal unit; IF-1; IF-3

Question 25

the shine-dalgarno or ribosome binding sequence (RBS) is ...

Answer 25

8-13 nt purine-rich element in mRNA where ribosomes bind to initiate translation

Question 26

although _____ is always the first amino acid in a prokaryotic protein, the second and each subsequent amino acids can be any one of the 20

Answer 26

fMet

Question 27

_______ binds charged initiator fMet-tRNA and escorts it into the P site

Answer 27

IF-2-GTP

Question 28

IF-2 hydrolyzes the GTP, resulting in ....

Answer 28

dissociation of all IFs

Question 29

the __________ binds forming the complete ___________. - the complex is now complete - ____________________: - A site is vacant - P site has fMet-tRNA - E site is vacant

Answer 29

50S subunit; 70S ribosome; translation initiaton complex

Question 30

_________________ act on the 70S ribosome

Answer 30

elongation factors (EFs)

Question 31

___________ binds an __________ in the cytoplasm and delivers this charged tRNA to the ribosomal A site. - base pairing occurs between the aminoacyl-tRNA anticodon and the second codon in the mRNA. - tetracyclines bind to the 30S subunit blocking aminoacyl-tRNA entry into the A site

Answer 31

EF-Tu-GTP; amino acyl-tRNA

Question 32

____________ hydrolyzes GTP-> GDP + Pi and exits - A site has an aminoacyl-tRNA - P site contains fMet-tRNA - E site remains vacant

Answer 32

EF-Tu-GTP

Question 33

EF-Tu-GDP is recycled to EF-Tu-GTP by _________

Answer 33

EF-Ts

Question 34

the ribosome is a ___________. - the free amino group on the acyl-tRNA in the A site attacks fMet-tRNA in the P site - fMet is transferred to nascent chain in the A site forming the first peptide bond

Answer 34

peptidyl transferase

Question 35

_____________ binds 50S subunit blocking peptidyl transferase activity

Answer 35

chloramphenicol

Question 36

the ________________ moves the mRNA through the cleft in the ribosome

Answer 36

EF-G GTP translocase

Question 37

___________ binds near the A site - GTP-> GDP shifts ribosome down one codon on the mRNA - A site is again vacant - P site contains dipeptidyl-tRNA - E site has an uncharged tRNA that quickly dissociates - _____________ binds to the 50S ribosomal subunit rRNA and blocks the binding site for EF-G

Answer 37

EF-G GTP; erythromycin

Question 38

___________ changes shape of rRNA in 30S subunit, causing ribosome to misread mRNA

Answer 38

streptomycin

Question 39

at a stop codon, the ribosome ...

Answer 39

pauses and waits for a new charged tRNA

Question 40

a ___________ recognizes the stop codon and binds to the A site (essentially tricks ribosome into thinking its a charged tRNA) - ____________ activate peptidyl-transferase hydrolyzing the peptidyl-tRNA bond terminating translation

Answer 40

release factor (RF)

Question 41

_____________ and ______ dissociate the complex ______ rebinds to 30S subunit

Answer 41

ribosome recycling factor (RRF) and EF-G; IF-3

Question 42

how is eukaryotic translation different from prokaryotic translation?

Answer 42

mRNAs are synthesized and RNA processed in the nucleus - mRNA is transferred to the cytoplasm where it may be intercepted by miRNA-RISC

Question 43

the __________ carries out translation. (eukaryotes)

Answer 43

80S ribosome

Question 44

eurkaryotic translation initiation complex - ____ brings charged Met-tRNA to the _____________ before the mRNA - ____ complex binds to the mRNA 5' cap and brings it to the 40S - the ribosome scans the mRNA 5'->3' to locate the AUG within a ______________ - ___________ binds to complete the _____________

Answer 44

eIF2; 40S subunit; eIF4; Kozak sequence; 60S subunit; 80S ribosome