Chapter 15: The Genetic Code and Translation

Question 1

What is the bond that joins amino acids?

Answer 1

peptide

Question 1

What is the wobble position?

Answer 1

3rd base pairing on codon is relaxed and causes degeneracy in the genetic code

Question 2

What are the combination positions of the wobble hypothesis?

Answer 2

Anticodon: C, Codon: G
Anticodon: G, Codon: U/C
Anticodon: A, Codon: U
Anticodon: U, Codon: A/G
Anticodon: I, Codon: A/U/C

Question 3

What are the four macromolecules in tln?

Answer 3

1. ribosomes
2. amino acid activating enzymes
3. tRNA
4. soluble proteins (tln factors)

Question 4

What is aminoacyl tRNA synthetase?

Answer 4

An enzyme that binds specific tRNAs with their specific amino acid and charges it

Question 5

What is the two step reaction of aminoacyl tRNA synthetase?

Answer 5

1. amino acid reacts with ATP
2. Amino acid is transferred to tRNA

Question 6

What is a tRNA structure?

Answer 6

Anticodon of tRNA pairs with codon of mRNA, amino acid is covalently attached to 3’ end of tRNA

Question 7

What are the steps (6) of initiation in tln in prok?

Answer 7

1. IF-3 binds to small subunit of ribosome, prevents large subunit from binding
2. small subunit attaches to mRNA
3. charged tRNA (fmet) forms complex with IF-2 and GTP
4. IF-1 binds to small subunit and tRNA/IF-2/GTP complex binds to initiation codon
5. all initiation factors dissociate and GTP is hydrolyzed to GDP + Pi
6. large subunit joins to create 70S initiation complex

Question 8

What are the names for the ribosomal subunits?

Answer 8

Large (50s) - EPA
Small (30s)

Question 9

what are the 3 sites of the 50s subunit?

Answer 9

E (exit)
P (peptidyl)
A (aminoacyl)

Question 10

What is the difference during initiation in tln in euk?

Answer 10

• not fmet just met
• no shine-delgarno
• kozak sequence
• Poly a tail interacts with 5’ cap via cap binding proteins to promote tln initiation

Question 11

What are the (7) steps of elongation in tln?

Answer 11

1. fmet tRNA occupies P site of 50s
2. Ef-Tu GTP and a charged tRNA form a complex and enter the A site of 50s
3. GTP is cleaved to GDP +Pi and Ef-Tu GDP complex is released
4. peptide bond forms between amino acids in P and A site, tRNA in P site releases AA
5. ribosome moves down mRNA to next codon which requires EF-G and GTP
6. tRNA that was in P site now in E site and exits
7. tRNA that occupied A site is now in P site

Question 12

What are the (4) steps of termination in tln?

Answer 12

1. when ribosome tlts a stop codon, RF-1 enters P-site and RF-3/GTP complex attach to ribosome
2. polypeptide is released
3. GTP is hydrolyzed to GDP
4. tRNA, mRNA and release factors are released from ribosome