All of the DNA present in embryonic stem cells (and in the fertilized egg, for that matter) is present in adult cells. The difference is that various genes affecting cell behavior are activated and deactivated during the course of development. Specifically, the genes allowing cells to differentiate into multiple forms are activated by chemical signals during embryonic development, then deactivated by other signals as the different cell types become fully formed.

http://biology.kenyon.edu/courses/biol114/Chap11/Chapter_11.html

The reason why animals such as salamanders can regenerate lost limbs is that the initial response to the amputation includes the formation of a cell layer which signals other cells to move into the wound. It was long thought that these cells were induced to dedifferentiate, forming a mass of cells (blastema) which would then form the skeleton, nerves, blood vessels, muscles, and skin of a new limb. (In humans, the initial response is similar on a cellular level, but the wound fills with scar tissue instead of signaling cells.)

http://www.scientificamerican.com/article.cfm?id=regrowing-human-limbs

However, a recent study indicates that the blastema cells are not true stem cells. Instead, they are derived from tissue-specific stem cells and can only regenerate the original cell type.

http://www.technologyreview.com/biomedicine/22955/

Humans also have tissue-specific stem cells, and spontaneous regeneration of lost fingertips has been observed in children, so it would appear that the genetic *potential* for limb regrowth is present in humans as well.

http://en.wikipedia.org/wiki/Regeneration_(biology)#Regeneration_of_human_skeleton

Unfortunately, turning that potential into reality won't be easy. The specific genes involved would have to be identified (since they're inactive, many of the usual techniques for identifying genes won't work), and then their specific activation mechanisms would have to be discovered. Only then would we know whether it's even possible to enable humans to regrow missing limbs.

this is because of the cell fate of stem cells. as you see, in some animals like the lizards they can regenerate the whole organ because their stem cells can differentiate into the rest of tissues required. As for humans, this is not possible. the good news, however, now we can make these cells change into other sorts of cells and tissues. but this science is still in the begining. so i think in a few years we might hear interesting discoveries in this field.
As for your question regarding DNA. the reason that our stem cells can't always change into other types of cells is because they are programmed to do so. They have instructions on their DNA that tells them they can't change. The fun part is that some scientists were able to manipulate these instructions! i remember an article in science magazine (website below) where only four genes were enough to manipulate a normal (somatic) cell into a stem cell!

http://www.sciencemag.org/cgi/content/abstract/318/5858/1917

I think the human bodies ability to repair itself is pretty amazing. Unfortunately we can't regenerate a limb or a knocked out tooth like some animals can but that's not actually DNAs fault because there are animals (with DNA) who can do such things.

It just turns out that humans evolved in an environment where that ability was not particularly important. Maybe because we have other humans to help us in such situations, maybe because we are smart enough to avoid serious injury more than other animals.

Scientists are learning a great deal about limb regeneration, maybe someday it will be possible in humans.