Ammonia and DNA samples?

Question

I saw the movie Boondock Saints not too long ago (I'd recommend it for any who haven't seen it). Toward the end of the movie, the two protagonists (who are extremely lucky crime-fighting vigilantes) use a spray-bottle of ammonia to cover up their spilled blood. Somehow, this made it impossible for forensics to acquire a DNA sample from those blood-spots, when they appeared in a later scene.

If I had to guess, I'd say that ammonia [is supposed to, in the movie] neutralize DNA, because ammonia is a base and DNA is an acid ("DNA" stands for "deoxyribonucleic acid")

So my question is: can ammonia neutralize DNA or otherwise make it impossible to take a sample? Or is it really just diluting it to a point where taking a sample is nearly impossible?

In asking this I also remember that urine has a high ammonia content, yet, to my knowledge, I don't think this prevents anyone from acquiring DNA samples from urine.

Answer 1

I think you're overanalyzing this.

Ammonia is a strong base. Strong bases and acids are going to change molecules/ break chemical bonds no matter what they are.