Translation

Question 1

How many possible codons are there?

Answer 1

64

Question 2

What is a triplet binding assay?

Answer 2

A test which proves synthetic trinucleotides can promote binding of specific tRNAs to ribosomes.

Question 3

How many sense codons are there?

Answer 3

61

Question 4

Where is the code not universal?

Answer 4

In mitochondria

Question 5

What is tRNA?

Answer 5

The adaptor between codons and amino acids.

Question 6

How does the tRNA link to its amino acid?

Answer 6

Through covalent bonding.

Question 7

What part of the tRNA recognises the codon?

Answer 7

The anticodon

Question 8

What defines the cloverleaf structure of tRNA?

Answer 8

4 stems and 4 loops

Question 9

What do the hydrogen bonds between paired bases of the tRNA result in?

Answer 9

Its 3D structure

Question 10

What is the open reading frame?

Answer 10

The protein coding sequence in a gene.

Question 11

What is meant by the genetic code being degenerate?

Answer 11

Most amino acids have more that one codon.

Question 12

What happens to the tRNA when it binds the amino acid?

Answer 12

It becomes charged

Question 13

How does the tRNA associate with the mRNA molecule?

Answer 13

Through the anticodon loop

Question 14

What is the function of aminoacyl-tRNA synthetase?

Answer 14

It catalyses the covalent linkage between the 3’ end of the tRNA and its cognate amino acid.

Question 15

Which tRNAs does aminoacyl-tRNA synthetase recognise?

Answer 15

All isoaccepting tRNAs

Question 16

How many aminoacyl-tRNA synthetases are there?

Answer 16

One per amino acid

Question 17

What did Seymour Benzer discover?

Answer 17

That protein synthesis machinery recognises the anticodon not the amino acid associated with the tRNA.

Question 18

What led Seymour Benzer to their discovery?

Answer 18

A cysteine charged tRNA was chemically changed to become an alanine charged tRNA. Alanine was then incorporated into the polypeptide chain instead of cysteine.

Question 19

What parts of translation are subject to proofreading?

Answer 19

Amino acid selection and tRNA selection.

Question 20

What is the process of kinetic proofreading?

Answer 20

If the wrong amino acid is selected the forward reaction is disfavoured and so slows.

Question 21

What is the process of chemical proofreading?

Answer 21

If the wrong amino acid is selected the catalytic reaction is reversed.

Question 22

What does proofreading avoid?

Answer 22

The need for absolute accuracy.

Question 23

What do sticky mutations result in in mice?

Answer 23

A neurodegenerative disease

Question 24

At what loci were sticky mutations found?

Answer 24

In the AlaRs gene encoding alanyl-tRNA synthetase.

Question 25

What can a defect in proofreading lead to?

Answer 25

A higher level of ser-tRNA ala synthesis (mis charging with serine)

Question 26

How many tRNA molecules are there?

Answer 26

Around 30

Question 27

What allows one tRNA to decode more than one codon?

Answer 27

Wobble and modified bases.

Question 28

What is the wobble hypothesis?

Answer 28

Watson-Crick base pairing rules between anticodon position one and codon position three are relaxed due to flexibility and modifications of the anticodon loop.

Question 29

What is the structure of ribosomes?

Answer 29

It consists of two subunits. The larger subunit has three rRNA molecules and 49 different proteins in a precise pattern. The smaller subunit has one rRNA and 33 proteins.

Question 30

How are ribosomal subunits held together?

Answer 30

By ionic and hydrophobic forces.

Question 31

What forms the bulk of RNA structure in bacteria?

Answer 31

The 50s crystal

Question 32

What fills the gaps between rRNA?

Answer 32

Proteins

Question 33

What catalyses peptide bond formation?

Answer 33

The 23s rRNA (ribozyme)

Question 34

How many tRNA binding sites are there on the largest ribosome subunit?

Answer 34

Three

Question 35

Where do codon-anticodon interactions between tRNA and mRNA occur?

Answer 35

At the P and A sites

Question 36

What is the function of the A (aminoacyl tRNA/entry) site?

Answer 36

It binds the anticodon to the charged tRNA.

Question 37

What is the function of the P (peptidyl tRNA/donor) site?

Answer 37

It is where the tRNA adds the amino acid to the growing peptide chain.

Question 38

What is the function of the E (exit) site?

Answer 38

It is where the tRNA sits before being released from the ribosome.

Question 39

What are the stages of translation?

Answer 39

Initiation, elongation and termination