Question

A portion of a protein-coding gene is provided for this question. Given the non-template DNA sequence of 5'-TACTATGCTGAGCATTATTGCTAAGTGATGGCTA-3':

a. Write the complementary template DNA sequence in a 5' to 3' direction.

b. Write the mRNA sequence that would be transcribed from this segment of DNA in a 5' to 3' direction.

c. Starting from the first start codon, write the polypeptide sequence that would be translated from the mRNA sequence.

d. Define the following terms in your own words: frameshift mutation, point mutation, missense mutation, nonsense mutation, silent mutation, transition mutation, transversion mutation.

e. An individual is exposed to a chemical mutagen and has a change in their DNA so that the non-template sequence is now 5'-TACTATGCTGAGCACTATTGCTAAGTGATGGCTA-3'.

a. Which type(s) of mutations fit this change in the given DNA sequence? Explain your choice based on the sequence change and on your definitions above.

b. Write the new polypeptide sequence that would be produced from this change, beginning from the first start codon.

c. Since this mutation occurred later in life within a cell in the individual's kidney, will the mutation be heritable? Explain your answer.

Answer 1

Given the DNA sequence is

5'-TACTATGCTGAGCATTATTGCTAAGTGATGGCTA-3'

a. The complementary DNA sequence will be:

         3’- ATGATACGACTCGTAATAACGATTCACTACCGAT-5’

          Thus the strand in 5’ to 3’ direction will be:

      5’- TAGCCATCACTTAGCAATAATGCTCAGCATAGTA-3’

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b. mRNA sequence in 5’ to 3’ direction will be:

5’ – UACUAUGCUGAGCAUUAUUGCUAAGUGAUGGCUA-3’

it will be same as the non template strand, only T will be replaced by U.

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C. The polypeptide sequence from the first start codon AUG will be:

5’ – UACUAUGCUGAGCAUUAUUGCUAAGUGAUGGCUA-3’

Met-Leu-Ser-Ile-Ile-Ala-Lys-Stop