Question

3.

Below are several DNA sequences that are mutated compared with the wild-type sequence:

3’ - T A C T G A C T G A C G A T C - 5’.

Each is a section of a DNA molecule that has separated in preparation for transcription, so you are only seeing the template strand.

a. Construct the complementary DNA sequences (indicating 5’ and 3’ ends) for each mutated DNA sequence.

b. Transcribe (indicating 5’ and 3’ ends) the template strands.

c. Translate the mRNA molecules using the genetic code, recording the resulting amino

acid sequence.

d. What type of mutation is each?

Mutated DNA Template Strand #1: 3’ - T A C T G T C T G A C G A T C - 5’

Complementary DNA sequence:

mRNA sequence transcribed from template:

Amino acid sequence of peptide:

Type of mutation:

Mutated DNA Template Strand #2: 3’ - T A C G G A C T G A C G A T C - 5’

Complementary DNA sequence:

mRNA sequence transcribed from template:

Amino acid sequence of peptide:

Type of mutation:

Mutated DNA Template Strand #3: 3’ - T A C T G A C T G A C T A T C - 5’

Complementary DNA sequence:

mRNA sequence transcribed from template:

Amino acid sequence of peptide:

Type of mutation:

Mutated DNA Template Strand #4: 3’ - T A C G A C T G A C T A T C -5’

Complementary DNA sequence:

mRNA sequence transcribed from template:

Amino acid sequence of peptide:

Type of mutation

Answer 1

both strands of the DNA are complementary to each other A base pairs with T, G basepairs with C, RNA polymerase adds nucleotides complementary to the template strand A is complementary to T, U is complementary to A and G is complementary to C and C is complementary to G.

a) Complementary DNA sequence: 5`-ATGACTGACTGCTAG-3`

b) mRNA sequence transcribed from template: 5`-AUGACUGACUGCUAG-3`

c) Amino acid sequence of peptide: Met-Thr-Asp-Cys

d)

Mutated DNA Template Strand #1: 3’ - T A C T G T C T G A C G A T C - 5’

Complementary DNA sequence:   5`-ATGACAGACTGCTAG-3`

mRNA sequence transcribed from template: 5`-AUGACAGACUGCUAG-3`

Amino acid sequence of peptide: Met-Thr-Asp-Cys

type of mutation: silent mutation the second codon has changed but the amino acid does not change

Mutated DNA Template Strand #2: 3’ - T A C G G A C T G A C G A T C - 5’

Complementary DNA sequence:   5`-ATGCCTGACTGCTAG-3`

mRNA sequence transcribed from template: 5`-AUGCCUGACUGCUAG-3`

Amino acid sequence of peptide: Met-Pro-Asp-Cys

Type of mutation: Missense mutation, the second codon has changed so the second amino acid is also changed, the single base substitution which the codon and the amino acid is missense mutation.

Mutated DNA Template Strand #3: 3’ - T A C T G A C T G A C T A T C - 5’

Complementary DNA sequence: 5`-ATGACTGACTGATAG-3`

mRNA sequence transcribed from template: 5`-AUGACUGACUGAUAG-3`

The amino acid sequence of peptide: Met-Thr-Asp

Type of mutation: Non-sense mutation, the fourth codon is changed to a stop codon due to a single base substitution.

Mutated DNA Template Strand #4: 3’ - T A C G A C T G A C T A T C -5’

(T at the third position is deleted)

Complementary DNA sequence: 5`-ATGCTGACTGCTAG-3`

mRNA sequence transcribed from template:5`-AUGCUGACUGCUAG-3`

Amino acid sequence of peptide: Met-Leu-Thr-Ala

Type of mutation: frameshift mutation, Frameshift mutation is due to the deletion or insertion of nucleotides which are not in the multiples of three, changes the reading frame from the point of insertion.