for the normal DNA sequence, since thymine (T) binds with adenine(A) and Adenine(A) binds with uracil(U) because there is no thymine is RNA guanine(G) pairs with cytosine(C) :
normal DNA:TACCCCGTGCAT ATAT CATATAGCACT
normal mRNA:AUG GGG CAC GUA UAU AGU- AUA UCG UGA
i grouped letters in threes as codons
normal Protein:methionine-glycine-histidine-valine-Tyrosine-Serine-Isoleucine-serine-stop
mutated DNA:TACCCCGTGCACATATCGTATAGCACT
mutated mRNA:AUG GGG CAC GUG UAU AGC AUA UCG UGA
mutated protein:methionine-glycine-histidine-leucine-Tyrosine-Serine-Isoleucine-Serine-stop
In the mutated protein valine is replaced with leucine. Those two amino acids have different radicals that perform different functions so the protein will have an altered function.