Question

Given the Normal DNA Sequence: 5’ –ATG ATC AGA CTA GCT CAC TCG GGA GTG TGA… 3’

Determine what type of mutation occurred in the following mutant DNA.

Mutant I: 5’ –ATG ATC AGA CTA GCT CAC TCG TGA GTG TGA… 3’

a. At what codon number did mutation occurred?

b. Identify the type of substitution point mutation happened

c. What is the resulting amino acid of the codon that was mutated?

d. What is the consequence of that mutation?

Answer 1

Ans a) The mutation occurred at 22nd codon number. GGA in original DNA sequence is changed or mutated to TGA.

Ans b) Since Guanine (from normal DNA sequence) is mutated to Thymine (in mutated DNA sequence) i.e change of purine to pyrimidine is known as Transversion mutation.

Ans c) GGA (in normal DNA sequence) when trancribed results in CCU which codes for Proline amino acid.

TGA (in mutated DNA sequence) when transcribed results in ACU which codes for Threonine amino acid.

Ans d) Since in normal DNA sequence,CCU codes for Proline ( Non-polar amino acid) and in mutated DNA sequence, ACU codes for threonine (Polar amino acid due to the presence of OH group in the side chain). The stability of the molecule will be affected due to this mutation. Noramally, non-polar amino acids are found inside and polar amino acids are found on the exterior so that the OH group will interact with the water or aqueous environment.But,due to such mutation Non-polar amino acid is replaced by Polar amino acid.