The Genetic Code

Question 1

Mutation in DNA sequence leads to…

Answer 1

Change in amino acid sequence

Results in completely different proteins usually

Question 2

N-terminus?

Answer 2

Refers to start of amino acid chain synthesized form the tRNA and the ribosome.

Characterised by the NH3+ at the start of the chain.

Question 3

C-terminus?

Answer 3

Refers to the end of the amino acid chain

Characterised by the free carboxyl (COO-) group at the end of the chain.

Question 4

How many types of amino acids do humans use to build proteins?

Answer 4

20 types

Question 5

How may nucleotides code for one amino acid?

Answer 5

3 nucleotides

This represents a codon.

Question 6

Define degenerate

Answer 6

More than one type of triplet code codes for the same amino acid

Question 7

Is the genetic code universal?

Answer 7

Yes, but there are slight differences in the mitochondrial code

Question 8

Site of translation?

Answer 8

Ribosome

Question 9

Which molecule is responsible for recoginsing codon sequences on the ribosome?

Answer 9

tRNA - transfer RNA

Question 10

Which loop of tRNA contains the anticodon sequence?

Answer 10

Loop II

This sequences binds to the right codon in mRNA

Question 11

tRNA binds to the first two bases of a codon strongly but…

Answer 11

there is less specificity for the third base of the codon.

It can bind to multiple bases which means tRNA is slightly more flexible with its pairing.

Question 12

What catalyses the reaction (binding) between an amino acid and a specific tRNA molecule?

Answer 12

Aminoacyl-tRNA synthetase

This charges the tRNA in order to make it more reactive towards the amino acid.

Question 13

AMP on the enzyme allows L-shape to be exposed to tRNA…

Answer 13

tRNA binds to the the L-shape structure

Question 14

Aminoacylation?

Answer 14

This is when AMP is displaces and AA binds to the tRNA.