If shapeshifters can change their appearance and DNA...?

If shapeshifters can change their appearance and DNA, then can't they copy someone else's powers too? And if so, why don't they lose their previous ability (shapeshifting) if they completely change their DNA to match someone else?

Well you see, shapeshifting is not changing your DNA, just your shape and coloration. So when that happens, they are still genetically identical to what they were before they changed, so they can still shapeshift, and that is also why they cannot copy powers.

@Charetter115: Hmmmm, that is a good point, but i am not sure if that is completely true. I think they do alter their DNA when they shapeshift because they do change their shape and coloration because how would you explain shapeshifters that shapeshift into animals. Some animals produce poison and webs that are only chemically produced due to their body's genes. How would shapeshifters such as Beast Boy use those traits if he/they do not alter their gene during the process? And, genes affect an animal and human's body structure and muscles and thus affect the animal's strength because a gorilla is obviously stronger than a human because of their muscles.

Also, when shapeshifters, like Martian Manhunter, change into another human they are altering the size of their bone structure, therefore changing their internal parts, since, some people have a bigger ribcage than others or their heads or smaller or larger. And, their organs differ in size. All of these must be taken into account if the human size is different. Not everyone will have the same body structure as the shapeshifter. They must be altering their gene, but would this affect their power if their power stems from their original gene?

And I was mainly curious about those shapeshifters that could copy powers and i was wondering what would happen to their original power (shapeshifting) if they copy someone else's gene.