Protein Synthesis

Question 1

mRNA is made from what strand, but is identical to which strand?

Answer 1

Made from template strand, but is identical to coding strand.

Question 2

WHat are codons? Read from which direction?

Answer 2

Triplet nucleotides that code for amino acids. Read from 5’ to 3’ direction.

Question 3

What is the start codon? Reading frame?

Answer 3

AUG (Met)s. Reading frame starts at start codon and ends at stop codon.

Question 4

What is monocistronic and polycistronic?

Answer 4

Mono: Eukaryotes only have one coding region/mRNA
Poly: Prokaryotes have multiple coding regions/mRNA

Question 5

Silent, missense, nonsense, splice site, and frame-shift mutations?

Answer 5

1. Silent=Change in codon, no change in sequence
2. Missense=Change in codon, change in sequence
3. nonsense=change in codon,change to a stop codon
4. Splice: Alters how introns are removed
5. Insertion or deletion leading to different frame.

Question 6

What does tRNA do? What are the different parts of it?

Answer 6

it reads the codons. Acceptor site is where amino acids links. Anticodon site is were it pairs with the codon in mRNA.

Question 7

Which end of the tRNA is the amino acid attached?

Answer 7

3’ end.

Question 8

Ribosomes are made up of what? What subunits?

Answer 8

rRNA. 30 S and 50 S subunits

Question 9

WHat are the stages of protein synthesis?

Answer 9

1. Activation of amino acid
2. Initiation
3. Elongation
4. Termination

Question 10

What couples amino acids to their cooresponding tRNA? What does it use?

Answer 10

aminoacyl-tRNA synthetase. Uses ATP

Question 11

What is the shine-delgarno sequence?

Answer 11

Purine rich sequence upstream of start codon that helps orient the tRNA.

Question 12

Initiation of protein synthesis requires what?

Answer 12

30s and 50s ribosomal units, mRNA, fMET-tRNA, GTP, Mg+2, Initiation factors.

Question 13

What are the steps of protein synthesis initiation?

Answer 13

1. 30s unit binds to mRNA with Initiation factors.
2. fMET-tRNA orients and binds with IFactors, GTP used.
3. 50s subunit with IFactors.

Question 14

What are the steps of protein synthesis elongation? What does it require?

Answer 14

1. Binding of incoming aminoacyl-tRNA
2. Peptide bond formation
3. Translocation
   Requires GTP, elongation factors

Question 15

What happens during the termination step of protein synthesis?

Answer 15

Release factors hydrolyze terminal bond and releases the polypeptide, ribosome dissociates.