The Genetic Code

Question 1

How many codons are there?

How many code for amino acids?

Answer 1

64

61

Question 2

What is the in-vitro translation system?

Answer 2

System in a test tube that allows synthesis of proteins. E. Coli mRNA is removed and the required mRNA strand is inserted. The E. Coli produces protein using the introduced strand.

Question 3

What are the three stop codons?

Answer 3

UAA, UAG, UGA

Question 4

The genetic code is unambiguous, with the exception of one codon. What codon?

Answer 4

AUG- methionine and start codon.

Question 5

The genetic code in universal. However, there are some exceptions. What’s an example of an exception?

Answer 5

Mitochodria’s genetic code.

Question 6

What is the adaptor molecule in translation?

Answer 6

Aminoacyl-tRNA

Question 7

Where on tRNA is the amino acid attached?

Answer 7

3’ end

Question 8

What modifications are made to tRNA before it is made functional?

Answer 8

• 1 in 10 nucleotides are modified for interaction with other molecules.
• Introns need to be removed from where the anticodon is.
• A sequence is cut off the 5’ end
• The 3’ end is modified to expose the CCA sequence that covalently binds to amino acids.

Question 9

What enzyme catalyses the formation of aminoacyl-tRNA? How many of these are there?

Answer 9

tRNA/aminoacyl synthetase complex. One for each amino acid.

Question 10

Where does the energy required for formation of the bond between tRNA and the amino acid come from? What happens to the energy released when this bond is broken?

Answer 10

4ATP molecules –> 4AMP + 4PPi

Used for peptide synthesis at the ribosome.

Question 11

Which part of the amino acid is involved in the covalent bond between the amino acid and tRNA?

Answer 11

COOH.