A common argument of creationists is that mutations only cause loss in information, not progression, not advancement of a species, not additions to the code. Firstly genes are only information in the way we determine them as information, we apply the information. So we have to forgive how wrong this statement is. Genes are information the same way a stream is information, we assign the name to the stream, we put it on maps, we give it information. Genes are simply used in biological processes as a way to build proteins.
Evolution is small mutations selected for or against by natural selection. A vast majority of these mutations are neutral providing no immediate benefit, though they may build through successive generations to provide a benefit at a later stage (see salmonella's digestion of citric acid). Some of these mutations will be on the negative scale (from bad to terrible) some so bad the fetus may miscarry (around 50% of human pregnancy ends in miscarriage), others may infer an advantage in specific environments, eg colour blindness can assist in spotting camouflaged predators. Then again some maybe even slightly advantageous, taller, faster, smarter etc.
Lets think about knowledge.
Sometimes knowledge will come about due to incorrect information, this knowledge may persist for a time, it may never be tested and thus a group will hold it true even though it may not be, eg Iraq and it's supposed WMD's, thalidomide, everyone else's religious beliefs but your own. This incorrect knowledge could also use some assumption and be developed over time till it is discarded, eg the aether theory of space.
Sometimes correct knowledge will come about completely by chance, increasing the knowledge of humanity via a fluke, such as the supposed discovery of penicillin, tyre rubber etc.
Sometimes correct and thus valuable knowledge will develop over time based on many generations of work that has come before, Newton's famous word "I have seen so far as a I stood on a the shoulders of giants".
Regardless of how the knowledge is found or whether it is any good, it adds to the vast sum of human knowledge.
Obviously here I am comparing knowledge to DNA and life, it can take a long path of small iterative changes and flukes, but it can still add to the totality of diversity, it can to use the creationists phrase “add information” in that new knowledge is discovered by fluke or by iterative process. Saying knowledge can’t form this way as you don’t know where it came from is the same argument also used. But knowledge and evolution do exist even if we are not sure how they started, though we have some ideas, we may never know.
Like life, knowledge likely started in a very different form, with very different conditions than what we have today. It wasn’t humans that likely started knowledge, there is evidence that neanderthals had tool use (even modern chimps and Bonobos, even some birds show tool use), painted stories (there are elephants and birds that have shown this talent) and the use of fire (which lots of animals use to their benefit), there may have even been a rudimentary language that would have allowed the passage of ideas and thus a kind of natural selection on these ideas, with ideas that were important enough being iterated and reiterated through a young creatures upbringing.
Knowledge shows direct parallels with life, other people have noticed this before with the introduction of memetic theory and the very word meme. But I think this analogy goes the other way, and also points to the origin of knowledge as a parallel to the origin of life.
Some may claim that knowledge requires a mind, yes it does, even a rudimentary avian one. Life it would seem does not, life only requires a drive to replicate, something even the most simple single celled bacteria or proto-celled virus strives to do.
Some interesting things this brings up. Knowledge can develop similarly independently eg the idea itself of evolution driven by natural selection was developed a few times independently, akin to the eye and the many times it has evolved independently or the awesomeness that are slaters (Woodlice for the non-Australians), there is a case of very well defined convergent evolution, where two different animals evolved to look the same and live in the same environment, one the Woodlouse that is a crustacean, and one the pill millipede that is related to millipedes.
An idea can also develop once only, like gunpowder use (China), or the idea of having 0 or less (India), and then these ideas get spread around and were appropriated, akin to the eye again or bipedalism, although evolution can’t really take another creatures advantage and make it, its own. An idea can also develop once only (at least a further development) that then gets lost for ever, eg; Greek Fire, or Aztecs and their masonry, akin to the billions of creatures that have gone extinct in the history of earth.
So even if we grant DNA as information, information can change by accident, information can have an origin if we think about it, and information can be independent of an advanced mind. Information is different to DNA, DNA is just chemistry and demanding it needs a mind to contain it, is the same as demanding a twisting river demands a mind to explain its twists and turns, it obeys understood rules of fluid dynamics and flow, similarly DNA obeys rules of biological chemistry. If you claim these rules had to be given by a rule giver then you are simply shifting the burden and playing a God of the gaps, eventually the gap will be closed and you will have to retreat or simply deny the discovery.
Beyond all this babble, we have some interesting proof that a single mutation can make a big change, even with a "loss of information", in humans of all species; http://www.motherjones.com/politics/2014/01/bill-nye-creationism-evolution