Only if you ignore these factors:
There is a lot of DNA, sometimes called "junk" DNA. Although that name overstates the case, it is not generally expressed (read as a protein). Mutations there (and pre-existing oddities) will not generally express themselves, but such coding can do so if the right "start reading DNA code here" sequence is added.
For a given base pair, it is not always a case of, virtually everyone has, say, a "G" here, and any of the other 3 letters is a mutation. A given percent of people will have some other base pair, and as long as people don't have offspring with their siblings, that's rarely a problem even for "hamrful" mutations.
In the same way that a very short piece of computer code can call up a big subroutine and perform a complex function, a single base-pair mutation can cause a big difference in an organism's structure. While the fruit fly example where an extra pair of legs or wings pops up with a single mutation is not a useful feature, that doesn't mean that no such mutation could be helpful, given how many will occur.
Viruses can transfer larger pieces of DNA to radically different parts of ones chromosomes, and even between species. Large expressed sequences are not apt to be helpful, but some will.
If you had read post#659 you would know that 'junk DNA' is just one more evolutionist assumption which has been proven false. From the article by Baltimore on post#659:
The most discussed are coding regions that specify the sequence of proteins. Proteins are the actual machines that do the work of the body. The protein-coding regions are all that is captured by most metaphors for DNA. DNA as a book implies that all DNA has are letters that transform into words, the meaningful units of language, and that words are like proteins. But the regions of human DNA that encode proteins are only a few percent of the 3 billion-long string of letters. Most of it does other things. What are these other things?
The DNA code can specify the sites and nature of many different events. While we don’t know them all, there are easily 10’s of others aside from the sequence of proteins. For instance, DNA does not encode proteins directly, it uses an intermediary chemical string called RNA. Each RNA encodes one protein so an RNA is a form of packaging of the DNA string into meaningful, bite size pieces. But then the DNA must have a code for where to start an RNA, and where to end an RNA. The RNA is not used as a direct copy of DNA but rather is processed by destroying parts of it, modifying other parts and putting special structures at each end. There is code for each of these events.
a single base-pair mutation can cause a big difference in an organism's structure. . While the fruit fly example where an extra pair of legs or wings pops up with a single mutation is not a useful feature, that doesn't mean that no such mutation could be helpful, given how many will occur.
I already explained why the fruit fly's new wings were useless - because you need much more than a single mutation, a single gene to provide something useful. Read the 2nd paragraph on the quote above - the protein production needs more than the gene, much more. You are still following the discredited evolutionist assumption that the non-coding DNA is useless. Also check out the links in the article above on 'junk DNA' if you need more evidence.