Ch. 22a Translation (Final Exam)

Question 1

This type of RNA carries a series of codons to interact with tRNAs.

Answer 1

mRNA

Question 2

The coding strand is identical to the…

Answer 2

mRNA transcript

Question 3

The template strand is complementary to the…

Answer 3

mRNA transcript

Question 4

This type of RNA translates gene info to protein by delivering amino acids to the proteinsythesis center.

Answer 4

tRNA

Question 5

Where does the amino acid attach onto the tRNA?

Answer 5

Acceptor stem

Question 6

What is the function of the tRNA’s anticodon loop?

Answer 6

Recognizes specific complementary codons on mRNA

Question 7

What is the ribosome’s function?

Answer 7

Serve as docking station for tRNA that matches base sequences on mRNA

Question 8

What is the A site?

Answer 8

Binding site for the 1st amino acid

Question 9

What is the P site?

Answer 9

Binding site for peptidyl tRNA

Question 10

What is the E site?

Answer 10

Binding site for uncharged tRNA i.e. exit site

Question 11

Is the prokaryotic ribosome 70S or 80S?

Answer 11

70S

Question 12

Is the eukaryotic ribosome 70S or 80S?

Answer 12

80S

Question 13

What does initiation involve?

Answer 13

Binding of the ribosome to the mRNA to form initiation complex with 1st aminoacyl-tRNA

Question 14

What does elongation involve?

Answer 14

Addition of amino acids one at a time

Question 15

What does termination involve?

Answer 15

Dissociation of the ribosome from the mRNA

Question 16

This sequence is the purine-rich region of mRNA just upstream of the AUG start codon where the 30S subunit binds

Answer 16

Shine-Dalgarno sequence (AGGAGG)

Question 17

What are the 4 components of the initiation complex in E. coli?

Answer 17

1) 30S ribosome
2) mRNA template
3) 3 initiation factors
4) Aminoacyl-tRNA

Question 18

fmet-tRNA is the abbreviation for…

Answer 18

Aminoacyl-tRNA

Question 19

What is the purpose of aminoacyl-tRNA?

Answer 19

Recognizes start codons AUG, GUG, and occasionally UUG

Question 20

When does termination occur?

Answer 20

When a nonsense codon is encountered

Question 21

These protein factors allow the ribosomal subunits to dissociate from mRNA in prokaryotic termination?

Answer 21

Introduction of protein release factors that promote a hydration reaction, forcing the P-site amino acid to detach from tRNA

Question 22

While the subunits in prokaryotes bind directly to the initiation site, the subunits in eukaryotes…

Answer 22

Recognize the 5’ cap at the end of the mRNA and then move to the initiation site

Question 23

In prokaryotes, initiation factors set up initiation, but in eukaryotes, initiation is done by this sequence (HINT: ACCCAUGG).

Answer 23

Kozak sequence (ACCCAUGG)

Question 24

Do eukaryotic cells or prokaryotic cells have more initiation factors?

Answer 24

Eukaryotic

Question 25

Eukaryotic initiation factors are given this prefix to indicate their eukaryotic origin.

Answer 25

“e”

Question 26

While methionine, valine, and occasionally leucine act as start codons in prokaryotes, this 1 amino acid is the only start codon in eukaryotes.

Answer 26

Methionine

Question 27

What are the 3 main steps in eukaryotic elongation?

Answer 27

1) Positioning correct aminoacyl-tRNA
2) Forming peptide bond
3) Shifting mRNA by one codon relative to the ribosome

Question 28

In sum, when does elongation start?

Answer 28

When aminoacyl-tRNA enters the P-site