Genetic code

Question 1

What is a triplet code?

Answer 1

3 nucleotide bases in exon

Question 2

What is a codon?

Answer 2

3 mRNA bases complementary to the triplet code. The codon is complementary to the anti-codon found on tRNA

Question 3

How many triplet codes are there? How many different amino acids can be coded for?

Answer 3

64 triplet codes (4^3) = code is degenerate

20 different amino acids coded for

Question 4

What amino acids only have a single triplet code to specify them?

Answer 4

Methionine (Met) and tryptophan (Trp)

Question 5

What is the mRNA start codon?

Answer 5

AUG = start codon coding for methionine (met)

Question 6

What happens if the second base in the codon is pyrimidine?

Answer 6

Pyrimidine 2nd base (Cytosine or uracil) = hydrophillic amino acid coded for

Question 7

What happens if the second base in the codon is purine?

Answer 7

Purine 2nd base (adenine or guanine) = polar amino acid coded for

Question 8

Why is the genetic code ‘almost’ universal?

Answer 8

Mitochondria has its own DNA with different coding

Question 9

What happens if the 3rd base in a codon is mutated?

Answer 9

Has no effect on the protein - same protein coded for

Question 10

What happens if the 2nd base in a codon is mutated?

Answer 10

Causes a protein with similar properties to be coded for

Question 11

What is needed to start translation?

Answer 11

Start codon (Met) along with promoters and initiation factors

Question 12

How many base pairs are there in a gene?

Answer 12

1000 base pairs for every 1 gene

Question 13

What regions do initiation proteins bind to?

Answer 13

Initiation protections often bind to T-A rich regions = they only have 2H bonds and are weaker than G-C regions