Lec 22

Question 1

how are Amino acids joined together

Answer 1

joined together by peptide bonds to give primary protein structure

Question 2

Nirenburg and Mattaei

Answer 2

first to determine that a specific RNA sequence coded for a specific amino acid

procedure: Trinucleotide + ribosome+ 20 charged tRNAs (1 radioactive amino acid)
-allow binding to occur
-filter out unbound amino acids
-check to see if filter paper is radioactive
RESULT: filter paper is radioactive if the trinucleotide codes for the radioactive amino acid

conducted same experiment 20 times each using a different radioactive amino. If the protein is radioactive, then the labeled amino must be in the protein. For poly-U only the tube with 14C-he produced a radioactive protein therefore UUU codes for phenylalanine

Question 3

Wobble in the anticodon means

Answer 3

an anticodon containing inosine in the 5’ position to bind with 3 different codons.

Question 4

Degenerate

Answer 4

more than one codon can code for an amino acid

Question 5

No internal punctuation

Answer 5

no skip in the letter of the sequence

Question 6

Unambigous

Answer 6

codon AUG always codons for same amino acid

Question 7

Wobble hypothesis

Answer 7

a single tRNA can pair with more than one codon on mRNA

Question 8

What accounts for some but not all of the wobble?

Answer 8

inosine

Question 9

What are the four steps in translation

Answer 9

1. charging the tRNA
2. initiation
3. elongation
4. termination

Question 10

Aminonacyl Synthetase

Answer 10

enzyme that can put amino acid and tRNA together on 3’ end of the tRNA

Question 11

Initiation of translation

Answer 11

building a ribosome
-base pairing between shine-Dalgarno sequence of mRNA and 16s rRNA in the small ribosomal subunit

-base pairing between the AUG start codon on mRNA and the anticodon on charged tRNA

Ribosome now contains 3 new ties that can hold tRNA

Question 12

What are the 3 sites that ribosomes now contain after the initiation step of translation?

Answer 12

A site: aminoacyl
P site: peptidyl
E site: Exit

Question 13

What does initiator tRNA occupy?

Answer 13

occupies the P site in the 70S initiation complex

Question 14

Elongation: translation

Answer 14

PEPTIDYL transferase activity

-translocation-

Question 15

Peptidyl transferase activity

Answer 15

23S rRNA in the large subunit acts as a ribozyme to form the peptide bond between amino acids

ELONGATION

Question 16

Translocation

Answer 16

shifts so it can keep doing process until stop codon in a site

ELongation

Question 17

Termination: translation

Answer 17

stop codon arrives at A site

• release factor binds at sop codon
• protein is released from P site
• GTP hydrolysized to GDP + Pi for energy and all other parts dissociate

Question 18

Polysome

Answer 18

multiple ribosomes translating the same mRNA simultaneously

Question 19

Prokaryotic and Eukaryotic differences in initiation of translation

Answer 19

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