How do you predict that a change to a single nitrogen base, such as adenine or a thymine, could affect the function of a gene?

To replicate DNA or to translate DNA to RNA, you need to unzip the double helix and create an exact replica of the code. To do this, the nitrogen bases are strictly paired, A to T or U and C to G. The ends of these molecules match each other in such a way that a hydrogen bond, a strong intermolecular force, can form only between matching bases. Special proteins travel up and down the DNA strand facilitating the copying of the genetic code into RNA so that it can be decoded to create proteins.

Explanation:

I'm not 100% sure if this is what you're asking, but here you go hope it helps!

1 is the answer to this problem