Base changes in DNA?

Question

What type of base change in DNA might bring about the greatest change in a protein and the greatest phenotypic change immediately?

Answer 1

I would say a deletion in the structural gene would cause a frame shift mutation in which all of the preceding cordons will be read incorrectly during translation. Well on a cellular level the phenotypic change would be immediate if it was an important house keeping gene for example, phosphofructokinase a key regulatory enzyme of glycolysis. The cell would no long be able to efflux carbon down the glycolysis pathway and would no longer be able to metabolizes glucose.

Answer 2

I guess you are saying that a base change between that single base but it would not cause any form of frame shift. Just a typical substituition. I would say a change thymine to/from cytosine.

They look alike but they are actually different bases. A change in them would usually cause a difference in the formation of an amino acid. When there is a difference in the formation of the amino acid, there would be a great change in the folding and so on due to the difference in nature of amino acid.