tRNA and Codon-Anticodon Recognition

Question 1

List the three types of RNA that play major roles in translation.

Answer 1

1. mRNA
2. rRNA
3. tRNA

Question 2

What is the function of mRNA?

Answer 2

Codes for proteins

Question 3

What is the function of tRNA?

Answer 3

serve as adapters between mRNA and amino acids during protein synthesis.

Question 4

What is the function of rRNA?

Answer 4

form core of ribosome’s structure and catalyze protein synthesis

Question 5

What is the function of miRNA?

Answer 5

Regulate gene expression.

Question 6

How do tRNA molecules carry out their adapter function?

Answer 6

Carry a specific amino acid, recognizes specific codon, matches amino acid to codon.

Question 7

What does the anticodon loop of tRNA do?

Answer 7

Recognizes codon

Question 8

What does the 3’ end of tRNA do? WHat is its conserved sequence?

Answer 8

Covalently binds to amino acid; CCA

Question 9

How long is tRNA on average?

Answer 9

75 nucleotides.

Question 10

What are the five modified bases in tRNA?

Answer 10

N,N-dimethyl G, dihydro U, pseudouridine, 4-thiouridine, inosine.

Question 11

What is the purpose of tRNA having modified bases?

Answer 11

Helps with codon-anticodon recognition.

Question 12

Where does tRNA interact with mRNA?

Answer 12

Within the confines of the ribosome.

Question 13

Why is the anticodon said to be the reverse complement to the codon?

Answer 13

Complimentary to sequence of codon and written in reversed order

Question 14

Explain wobble pairing in tRNA.

Answer 14

Codon positions 1 and 2 pair with anticoding following Watson-Crick rules. Codon 3 base pairing can wobble, accepting unconventional base pairing.

Question 15

What can U wobble pair to in eukaryotes and prokaryotes?

Answer 15

A, G, or I for both.

Question 16

What can C wobble pair to in eukaryotes and prokaryotes?

Answer 16

G or I for both

Question 17

What can A wobble pair to in eukaryotes and prokaryotes?

Answer 17

P: U or I
E: U

Question 18

What can G wobble pair to in eukaryotes and prokaryotes?

Answer 18

P: C or U
E: C

Question 19

Which enzyme catalyzes tRNA charging?

Answer 19

Aminoacyl tRNA synthetases

Question 20

What is aminoacyl-tRNA?

Answer 20

tRNA charged with an amino acid

Question 21

How many aminoacyl-tRNA synthetases are there?

Answer 21

20; one for each amino acid

Question 22

How does the aminoacyl-tRNA synthetase charged the tRNA with an amino acid?

Answer 22

Covalently links carboxy end of amino acid to 3’-OH of 3’ A of tRNA.

Question 23

What is a class I aminoacylt-tRNA synthetase?

Answer 23

Amino acylation at 2’-OH of tRNA adenine. Amino acid then transferred to 3’ OH.

Question 24

What is a class II aminoacyl-tRNA synthetase?

Answer 24

Amino acylation directly at 3’-OH.

Question 25

What is the 2 step reaction in tRNA charging?

Answer 25

1. Amino acid covalently linked to ATP, generating aa-AMP
2. Amino acid transferred from aa-AMP to 3’ adenine of tRNA

Question 26

What are the two sites aaRS uses to selectively attach/remove amino acids?

Answer 26

1. Synthesis site
2. Editing site

Question 27

What is the role of the synthesis site in aaRS?

Answer 27

Amino acids that are too large cannot enter. Anything of the correct size or smaller gets added.

Question 28

What is the role of the editing site in aaRS?

Answer 28

Correct amino acid cannot enter the editing site. Incorrect ones enter and get cleaved off.