Below is an imaginary sequence of DNA. This sequence represents the sense strand

Question

Below is an imaginary sequence of DNA. This sequence represents the sense strand of the double helix. The first sequence is "wild type"; it has no mutations. Following that are five mutated sequences.

1.Transcribe the wild type sequence into mature mRNA and translate it into protein. Use this sequence as a reference for the rest of the activity.

2.Transcribe and translate each mutant sequence.

3.For each mutant sequence, identify the mutation and choose all of the following terms that apply:

Point Mutation

Frameshift Mutation

Insertion

Deletion

Base pair substitution

Silent Mutation

Missense Mutation

Nonsense Mutation

Provide your answers to #3, above, for each mutant sequence. For example, "In mutant sequence 1, the third base in the sequence is changed from C to T. This is a point mutation, base pair substitution, and changes the amino acid from alanine to proline, which is a missense mutation."

Please note that the sequences below are in UPPER CASE denoting the coding sequence only. There are no introns.

Wild type sense strand sequence

ATGTCACCCGCGCAGGAAGGA

Mutant 1

ATGTGACCCGCGCAGGAAGGA

Mutant 2

ATGTCAACCGCGCAGGAAGGA

Mutant 3

ATGCATTCACCCGCGCAGGAAGGA

Mutant 4

ATGTCACCCGCGCAGGAAGGC

Mutant 5

ATGTACCCGCGCAGGAAGGA

Wild type sense strand sequence

ATGTCACCCGCGCAGGAAGGA

Mutant 1

ATGTGACCCGCGCAGGAAGGA

Mutant 2

ATGTCAACCGCGCAGGAAGGA

Mutant 3

ATGCATTCACCCGCGCAGGAAGGA

Mutant 4

ATGTCACCCGCGCAGGAAGGC

Mutant 5

ATGTACCCGCGCAGGAAGGA

Explanation / Answer

1.

Wild type sense strand sequence

ATGTCACCCGCGCAGGAAGGA

mRNA sequence- 5'- AUGUCACCCGCGCAGGAAGGA (the sequence of the Sense strand of DNA is given; so the mRNA has the identical sequence - only U in place of T; the mRNA sequence is complementary to the antisense DNA strand).

peptide formed due to translation of the mRNA- Met-Ser-Pro-Ala-Gln-Glu-Gly.

2. & 3. (the answer is compiled together)

Mutant 1 - mRNA- 5' AUGUGACCCGCGCAGGAAGGA

peptide formed due to translation of the mRNA- Met.

Here, the fifth base C is changed to G; hence it is a base-pair substitution, point mutation & nonsense mutation (as a result of mutation, a stop codon arises which leads to the production of a truncated peptide).

Mutant 2- mRNA- 5' AUGUCAACCGCGCAGGAAGGA

peptide formed due to translation of the mRNA- Met-Ser-Thr-Ala-Gln-Glu-Gly.

Here, the seventh base C is changed to A; hence it is a base-pair substitution, point mutation & the amino acid proline is changed to threonine which is a missense mutation.

Mutant 3- mRNA- 5' AUGCAUUCACCCGCGCAGGAAGGA

peptide formed due to translation of the mRNA- Met-His-Ser-Thr-Ala-Gln-Glu-Gly.

Here, after the third base, three more bases CAU are inserted; hence it is insertion mutation but does not cause frameshift mutation ; only a new residue His is added between Met & Ser.

Mutant 4- mRNA- 5' AUGUCACCCGCGCAGGAAGGC

peptide formed due to translation of the mRNA- Met-Ser-Pro-Ala-Gln-Glu-Gly.

Here, the last residue A is changed to C; hence it is a point mutation, a base-pair substitution & here the amino acid Glycine remains as Glycine even after the mutation- hence it is a silent mutation.

Mutant 5- mRNA- 5' AUGUACCCGCGCAGGAAGGA (5'- AUGU*ACCCGCGCAGGAAGGA)

peptide formed due to translation of the mRNA- Met-Tyr-Pro-Arg-Arg-Lys-

Here after the fourth base, there is a deletion of a single base- leading to a frameshift mutation. Hence it is a frameshift mutation & a deletion mutation.

Wild type sense strand sequence

ATGTCACCCGCGCAGGAAGGA

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