3. Given the DNA sequences below of coding strands, identify and underline the m
ID: 61094 • Letter: 3
Question
3. Given the DNA sequences below of coding strands, identify and underline the mutation in each. What effect did each DNA mutation have on the final protein products. What type of mutation occurred (synonymous, nonsynonymous, nonsense, nonstop)? Explain.
Original DNA Sequence
5’ – A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’
Mutated Sequences
A. 5’ – A T G T T T T T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’
B. 5’ – A T G T T T G T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’
C. 5’ – A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A A – 3’
D. 5’ – A T G C T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’
E. 5’ – A T G T T T C T G G T C A A T T A G C G C A G G T C C A A C C T A G – 3’
F. Which of the above mutations do you think would be more deleterious to the cell/organism? Explain your reasoning.
Explanation / Answer
A. The given nucleotide sequence is, A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G.
The mutant sequence is, A T G T T T T T G G T C A A T T G C G C A G G T C C A A C C T A G.
In the above mutation, cytosine is replaced by thymine, turning CTG to TTG. Both TTG and CTG codes for leucine, so it does not affect the protein structure and function in any ways (remember that genetic code is redundant). This is an example of silent mutation.
B. The given nucleotide sequence is, A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G.
The mutant sequence is, A T G T T T G T G G T C A A T T G C G C A G G T C C A A C C T A G
In the above example, cytosine is replaced by guanine, turning the triplet code from CTG to GTG. GTG codes for valeine and CTG codes for leucine, this is an example of missense mutation. Missense mutations occur as a result of base substitutions, but the results are not much disruptive like nonsense mutations (Eg: they do not result in the formation of stop codons).
C. The given nucleotide sequence is, A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G.
The mutant sequence is, A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A A
In the above example, TAG is replaced by TAA, which is a stop codon. This is an example of nonsense mutation.
D. The given nucleotide sequence is, A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G.
The mutant sequence is, A T G C T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G
In the above example, insertion of cytosine after ATG, shifted the whole frame, which alters the whole sequence of protein. This is an example of frame shift mutation.
E. The given nucleotide sequence is, A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G.
The mutant sequence is, A T G T T T C T G G T C A A T T A G C G C A G G T C C A A C C T A G
In the above example, insertion of adenine in between T and G shifted the whole frame, which alters the whole sequence of protein. This is an example of frame shift mutation.
F. Of the above mutations, nonsense and frame shift mutations are more deleterious because they result in nonfunctional proteins.
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