11: Prokaryotic Transcription & Translation

Question 1

What genes are organized into operons?

Answer 1

Some prokaryotic genes

Question 2

What is the effect of greater RBS strength in an operon?

Answer 2

Producing more protein despite an equal amount of mRNA

Question 3

Can transcription stop at a stop codon?

Answer 3

No, it can only stop at a TX terminator

Question 4

Can translation of a protein be affected by a different gene’s RBS?

Answer 4

No

Question 5

What are the three phases of translation?

Answer 5

Initiation, elongation, and termination

Question 6

Are tRNAs transcribed from DNA?

Answer 6

Yes

Question 7

Do tRNAs encode amino acid sequences?

Answer 7

No, so they are not translated

Question 8

What carries amino acids to the ribosome?

Answer 8

tRNA

Question 9

What part of tRNA binds to mRNA?

Answer 9

Anticodons in tRNA bind to complementary codons of mRNA.

Question 10

What adds amino acids to tRNAs?

Answer 10

Aminoacyl-tRNA synthatases

Question 11

How many aminoacyl-tRNA synthetases are there?

Answer 11

20 - one for each amino acid

Question 12

Do aminoacyl-tRNA synthetases use the anti-codon to recognize their tRNAs?

Answer 12

No, they bind the acceptor stem of the tRNA

Question 13

Do different tRNAs for the same amino acid have similar or different acceptor stems?

Answer 13

Similar

Question 14

How can some tRNAs read multiple codons?

Answer 14

They wobble at the third position

Question 15

What two things are required for prokaryotic TL initiation?

Answer 15

An intiator factor and a special initiator tRNA

Question 16

What terminates translation by recognizing stop codons?

Answer 16

Release factors that enter the A pocket and bind a stop codon.

Question 17

Is the RBS transcribed?

Answer 17

Yes

Question 18

Could loss-of-function point mutations in an RBS theoretically be suppressed by point mutations in the 16S rRNA?

Answer 18

Yes because of the complementarity between the RBS and the 16S rRNA

Question 19

In what stage of translation is the finished polypeptide released to go and do its job in the cell?

Answer 19

Termination

Question 20

In what stage of translation does the ribosome gets together with the mRNA and the first tRNA so translation can begin?

Answer 20

Initiation

Question 21

In what stage of translation are amino acids brought to the ribosome by tRNAs and linked together to form a chain

Answer 21

Elongation

Question 22

What transfers the polypeptide from the tRNA in the P site to the new amino acid attached to the tRNA in the A site?

Answer 22

The peptidyltransferase activity of the ribosome

Question 23

How is tRNA along with the attached polypeptide translocated from the A site back to the P site?

Answer 23

With EF-G and GTP