What will happen if foreign DNA is injected into human?

We see hollywood flicks where we find transgenic monster in all forms,can we do that in real life as well.Can we make that happen in a laboratory ?

Let;'s say we want to create a mystical beast hybrid of tiger and human.So basically we need the DNA of a tiger to embed the quality of tiger into human.So we take out the DNA of tiger and inject it to human,so what will happen next are we going to get the stripes of tiger ,or the bloody claws??

Fact is nothing will happen, if the injection is not pure the most spectacular thing may be an immune response, and the extreme case an anaphylactic shock (and death).

Free floating DNA molecules in the blood stream are common, if they are somehow delivered inside the cell they would either cause the cell to die or recognized as foreign DNA and removed. In the intercellular space or blood I suspect that macrophages (type of immune cell) will eat all the tiger DNA

If you injected naked DNA from any species, nothing would really happen. The DNA would get degraded by cells of the immune system. If you injected a viral vector that infects human cells, and the viral vector carried a specific tiger gene, then the effects would depend on the viral vector and the gene, as well as which cells were targeted by the virus and incorporated the tiger gene. Even in this "gene therapy" or gene transduction scenario, not much would happen, as gene transduction has not been very successful and is not very easy to do in general, especially in humans. We can make transgenic mice carrying human DNA as models of some human diseases but then again the effects are limited to the specific gene in question. The mouse is still a mouse. If we made transgenic mice with a tiger gene, they would still be mice, behave like mice, etc.