Molecular Genetics: Translation

Question 1

prokaryotic vs. eukaryotic ribosomes

Answer 1

share a core or some proteins and rRNAs but also have unique proteins and rRNAs

Question 2

antibiotics as translation inhibitors

Answer 2

bind to unique proteins in prokaryotic ribosomes - won’t impact translation in human cells

Question 3

polyribosome

Answer 3

multiple ribosomes bound to a single mRNA

Question 4

ribosomes bind to which end of the mRNA

Answer 4

5’, read mRNA 5’ to 3’

Question 5

mRNP

Answer 5

export proteins + mRNA - docks and passes through nuclear pore in eukaryotes

Question 6

tRNA

Answer 6

adaptor molecule between amino acids and mRNAs (needed because hydrophobic amino acids can’t interact with negatively charged mRNA)

Question 7

where is the amino acid located on the tRNA

Answer 7

the 3’ end

Question 8

aminoacyl tRNA

Answer 8

amino acid bonded to its associated tRNA

Question 9

aminoacyl-tRNA synthetase

Answer 9

uses ATP to catalyze formation of ester linkage - different enzyme for each amino acid

Question 10

40 tRNAs pair with 61 amino acid coding codons supports

Answer 10

wobble hypothesis: flexibility in the third position for codon-anticodon pairing

Question 11

rules for wobble

Answer 11

G pairs with U or C
A pairs with U
Inosine pairs with U, C, or A only in tRNA

Question 12

active site in ribosomes

Answer 12

composed entirely of catalytic rRNA that aides in peptide bond formation

Question 13

ribozyme

Answer 13

RNA capable of acting as an enzyme

Question 14

translation initiation in prokaryotes

Answer 14

ribosome binding site binds to small subunit

Question 15

translation initiation in eukaryotes

Answer 15

small subunit binds to 5’ cap

Question 16

initiation factors

Answer 16

bring in the initial aminoacyl-tRNA

Question 17

translocation

Answer 17

ribosome shifts down the mRNA - requires GTP and help from elongation factor proteins

Question 18

translation termination

Answer 18

stop codon enters A site and protein release factor binds to the stop codon - ribozyme hydrolyzes ester linkage between tRNA and peptide chain and complex dissociates

Question 19

chaperone proteins

Answer 19

aide in protein folding

Question 20

4 methods of post-translational chemical modifications

Answer 20

sorting signals, (de)phosphorylation, methylation/acetylation, ubiquitination

Question 21

post-translational sorting signals

Answer 21

carb or lipid molecular address labels

Question 22

selenocysteine

Answer 22

amino acid that recognizes codon UGA (normally stop codon)

Question 23

how can selenocysteine be inserted into a peptide chain

Answer 23

selenocysteine insertion sequence must be in the 3’ UTR and assisting proteins must be present

Question 24

translational recoding

Answer 24

when a stop codon is used to insert amino acid - this method is being used by synthetic biologists to expand the genetic code