Translation

Question 1

What does tRNA do

Answer 1

Specifies which amino acid is coded for by which specific triplet codon

Question 2

Describe the structure of tRNA

Answer 2

• It is very short - 80 nucleotides
• single stranded
• Forms complementary base pairs with itself, folding into a clover leaf shape
• One end 3 nucleotides stick out providing a site for amino acid attachment
• One end has anti-codon which is 3 bases that are complementary to a specific mRNA codon

Question 3

As genetic code is degenerate, what does that mean for tRNA molecules

Answer 3

There are tRNA’s with different anticodons that can bind to the same amino acid

Question 4

What is the second stage of protein synthesis

Answer 4

translation

Question 5

What does translation involve

Answer 5

The transfer of genetic information from mRNA into amino acids

Question 6

How does mRNA enter the cytoplasm

Answer 6

Through the nucleur pores

Question 7

What does mRNA do when it enters the cytoplasm

Answer 7

mRNA associates with a ribosome, binding to the small subunit at the start codon (AUG)

Question 8

What occurs once mRNA has binding to small subunit on ribosome

Answer 8

The first tRNA molecule with the complementary anticodon (UAC) then binds to the start codon by hydrogen bonding

Question 9

What amino acid does the first tRNA molecule carry

Answer 9

methionine

Question 10

After tRNA has binded to the start codon what happens

Answer 10

The large sub-unit of the ribosome then binds and translation can begin

Question 11

What can occur once the ribosome is fully assembled

Answer 11

A second tRNA molecule with a complementary anticodon can bind to the next mRNA codon

Question 12

What happens once a second tRNA molecule with a complementary anticodon has bound to the next mRNA codon

Answer 12

A peptide bond is then formed between the 2 amino acids, forming a dipeptide and releasing methionine from the first tRNA

Question 13

What does the ribosome do once methionine is released from the first tRNA

Answer 13

It moves along the mRNA strand by exactly 3 base pairs (one codon) and the first tRNA is released back into cytoplasm ready to collect another amino acid

Question 14

What happens over time

Answer 14

Cycle repeats forming a long polypeptide

Question 15

What can occur once a ribosome has move along away from the start codon

Answer 15

Another ribosome is able to attach at the start codon

Question 16

What is the result of multiple ribosomes attaching to same mRNA strand

Answer 16

Many identical polypeptides are synthesised simultaneously from the same mRNA strand

Question 17

How does translation end

Answer 17

Their are no tRNA molecules with the complementary anti-codons for the stop-codons. This means no tRNA’s can bind and the synthesised polypeptide is released from the last tRNA molecule

Question 18

What happens to the ribosome when the stop codon is reached

Answer 18

The ribosome units separate from the mRNA strand and are quickly reused for another round of translation