Do you have proof that they are not. I thought mutations were just as likely to occur in non-functional sequences as otherwise. Since most DNA is dead code, that would mean most mutations have no effect at all.
You are absolutely wrong - and so is evolution. When the genome was finally deciphered, numerous parts of it did not contain genes. The evolutionists quickly jumped in with their explanation - this is junk DNA they said and the source for our evolution. Like the rest of the nonsense evolutionists have been saying for 150 years this "prediction" of evolution, has been proven wrong:
Conclusion
The idea that a major part of our DNA is "garbage" ignored the fact that a key feature of biological organisms is optimal energy expenditure. To carry enormous amounts of unnecessary molecules is contrary to this fundamental energy saving feature of biological organisms. Increasing evidence are now indicating many important functions of this DNA, including various regulatory roles. This means that this so-called non-coding DNA influences the behavior of the genes, the "coding DNA", in important ways. Still there is very little knowledge about the relationship between non-coding DNA and the DNA of genes. This adds to other factors making it impossible to foresee and control the effect of artificial insertion of foreign genes.
From: Junk DNA