Question

EXERCISE 1 MUTATION Work in a small group or alone to complete this exercise. In Lab 2, Exercise 8, you determined the amino acid sequence for the following strand of DNA: AGCAATCCGTCTTGG TCGTTAGGCAGAACC That strand has mutated. It is now AGCAACCCGTCTTGG TCGTTGGGCAGA ACC Use your knowledge of mutation and protein synthesis to answer the following questions 1. What mutation has occurred? 2. Will this mutation have a real effect? Why or why not? (Hint: You may want to try Exercise 10 from Lab 2 again, using the mutated DNA strand to make the mutated protein.)

Answer 1

Original DNA strand : A G C A A T C C G T C T T G G

   T C G T T A G G C A G A A C C

Transcription

   U C G U U A G G C A G A A C C ( As Thymine is replaced by Uracil in RNA )

Translation

Ser - Leu - Gly - Arg - Thr

Mutated DNA strand : A G C A A C C C G T C T T G G

   T C G T T G G G C A G A A C C

   Transcription

U C G U U G G G C A G A A C C

Translation

Ser - Leu - Gly - Arg - Thr

As there is single nitrogenous base is substituted i.e T with C in DNA molecule, the mutation present in the mutated DNA molecule is point mutation

After transcription and translation of the above original and mutated DNA molecule, we can observe that there is no change in the amino sequence. Hence protein function normally.

As there is change in the one nucleotide/nitrogenous base with another but there is no change in the amino acid sequence. Hence such type of mutations are known as silent point mutations.