This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Base substitution of GAC (Asp) to GAG (Glu) is an example ofa) Point mutationb) Silent mutationc) Non-sense mutationd) Conserved mutatione) Non-conserved mutation 
Select and explain. 
A. b, B. c, C. ad, D. ab
C: ad
Answer: C: ad 
Explanation: It is a point mutation because only single nucleotide is changed (C by G).
It is a conserved mutation because altered AA has same properties as the original one (Both are acidic).