06_Ribosome Assembly and Protein Synthesis

Question 1

How many frames are in each DNA strand?

Answer 1

3

Question 2

What is an open reading frame?

Answer 2

A region in the sequence of DNA that potentially encodes a protein

Question 3

How are rRNA genes arranged in a ribosomal gene cluster?

Answer 3

in tandem

Question 4

What are nontranscribed spacers?

Answer 4

sequences that separate transcription units in a ribosomal gene cluster

Question 5

Which arm of tRNA accepts amino acids?

Answer 5

Amino acid acceptor arm (3’ end)

Question 6

Which arm of the tRNA has unusual bases?

Answer 6

the T arm

Question 7

How does a tRNA recognize a codon sequence?

Answer 7

The anticodon on a tRNA complements the codon of the mRNA.

Question 8

What is the enzyme that adds an amino acid to tRNA? What is the energy source used? Which end (5’ or 3’) of tRNA is the amino acid added to?

Answer 8

aminoacyl tRNA synthetase
ATP hydrolysis
3’ end

Question 9

What is the wobble interaction in tRNA?

Answer 9

The nucleotide at the 5’ end of the tRNA anticodon can pair with more than one nucleotide at the 3’ end of the mRNA anticodon (3rd position)

Question 10

What is the wobble base pairing permitted with each of the following in the 5’ position of an anticodon?
G, A, U, I, C

Answer 10

G: U or C
A: U
U: A or G 
I: A, U, or C
C: G

Question 11

Which nucleotides in the wobble position of a tRNA anticodon can only base pair with one type of nucleotide on the mRNA codon?

Answer 11

A and C

Question 12

What is inosine? How does it compare to guanine?

Answer 12

it is a purine base most commonly found in tRNA; it is similar to guanine but is missing an -NH2.

Question 13

What are the three main steps of translation?

Answer 13

Initiation, Elongation, Termination

Question 14

Which sequence in prokaryotic mRNA guides the positioning of the small ribosomal subunit?

Answer 14

Shine-Delgarno sequence

Question 15

Which ribosomal subunit binds to prokaryotic mRNA first?

Answer 15

30S small ribosomal subunit

Question 16

What is the sequence of the initiation codon?

Answer 16

AUG

Question 17

Which initiation factors are necessary for the binding of the 30S ribosome to the prokaryotic mRNA initiation codon?

Answer 17

IF1 and IF3

Question 18

What is the tRNA in prokaryotes that recognizes the initiation codon?

Answer 18

formylmethionyl-tRNA

Question 19

Which initiation factor is required for association of formylmethionyl-tRNA with the initiation complex?

Answer 19

IF2-GTP

Question 20

How is IF2-GTP converted to its inactive form? How is it released from the complex?

Answer 20

Hydrolysis of the GTP to GDP+Pi by IF2 converts it to IF2-GDP and releases it from the complex.
This is an energetically-expensive, intrinsic activity.

Question 21

What are the A, P and E sites?

Answer 21

A: Aminoacyl-tRNA
P: Peptidyl-tRNA
E: Exit site