Translation

Question 1

Where does translation occur?

Answer 1

On the ribosome

Question 2

Does translation occur on the ribosome or in the ribosome?

Answer 2

On the ribosome

Question 3

What is a ribosome?

Answer 3

large complex of four RNAs and more than 80 proteins

Question 4

Th ribosome has a 3 sites which are between the large and small subunit of a ribosome. What are the sites?

Answer 4

• E site
• P site
• A site

Question 5

What is the large subunit of ribosome made up of?

Answer 5

49 proteins and 3 RNA molecules

Question 6

What is the small subunit of ribosome made up of?

Answer 6

33 proteins and 1 RNA molecule

Question 7

What is the E site?

Answer 7

exit site

Question 8

What is the P site?

Answer 8

peptidyl-tRNA site

Question 9

What is the A site?

Answer 9

aminoacyl-tRNA site

Question 10

What are the stages that translation can be broken down into?

Answer 10

• Initiation
• Elongation
• Termination

Question 11

Describe the initiation stage of translation:

Answer 11

• In eukaryotes, translation usually initiates at the first AUG codon in the mRNA
• Initiator tRNAmet bind to AUG start codon to small subunit
• Large subunit can bind and the ribosome to assemble
• P-site is filled by initiator leaving A site empty

Question 12

What will always be the first amino acid in the polypeptide chain?

Answer 12

Methionine

Question 13

In what order does translation occur of the three sites on a ribosome?

Answer 13

A to P to E

Question 14

Describe the elongation stage of translation:

Answer 14

• tRNA with anticodon that is complementary to codon in A site binds
• Amino acid on tRNA in P site is transferred onto the amino acid on tRNA in the A-site
• The empty tRNA mores to E site and is released
• There is a peptide tRNA in the A-site
• Ribosome slides down mRNA so tRNA with growing peptide can more to P-site
• A-site is free to bind another tRNA
• The cycles repeat until ready for termination stage

Question 15

Describe the termination stage of translation:

Answer 15

• At the end of the coding region of mRNA there is a STOP codon.
• No tRNA with STOP codon
• Translation ends
• Subunits disassemble and release the newly synthesised protein

Question 16

How do tRNA bound to amino acids?

Answer 16

Specific enzymes

Question 17

The binding of the tRNA and amino acid causes the tRNA to become?

Answer 17

Charged

Question 18

What part of the charged tRNA binds with the codon on the mRNA?

Answer 18

anticodon site on the tRNA

Question 19

How many bases correspond to an amino acid (thought experiment)?

Answer 19

• 4 types of nucleic acids
• 20 types of amino acids in proteins
• so 4^2 = 16 4^3 = 64
• Therefore, at least 3 amino acids
• If call combinations used then code must be degenerate

Question 20

How do we know codes don’t overlap?

Answer 20

As base mutations only ever affect one amino acids

Question 21

Describe the Crick, Brenner et als experiment:

Answer 21

• used bacteriophage T4 which infects Escherichia coli
• generated mutants in RII gene in bacteriphage
• distinctive large plaque
• Generated mutants in rII gene of bacteriophage T4 using proflavin

Question 22

What is proflavin?

Answer 22

• Planar molecule

- Intercalates between base pairs in DNA and can cause insertion or deletion of single base

Question 23

What is a codon?

Answer 23

Set of three nucleotides

Question 24

Can amino acids have more than one tRNA?

Answer 24

Yes

Question 25

What do we call it when one amino acid can have more than one tRNA?

Answer 25

Redundancy or degeneracy

Question 26

Do tRNAs have to have an accurate codon bind?

Answer 26

No, can have a mismatch on the third codon

Question 27

What is a bioinformatics?

Answer 27

Proteins sequence to be analysed digitally

Question 28

Why can the genetics code research effect the world?

Answer 28

As it is universal

Question 29

What is the genetic codes characteristics?

Answer 29

- Degenerate - Universal - Non-overlapping