The Unitrix is capable of storing the DNA of various different species. But unlike the completed Omnitrix, she can only hold one DNA sample at a time. You come with a module that can upload DNA you hold onto a selected Server.
You can copy the powers and abilities of different animals and then manifest the traits of these animals without changing your form.
You have full control over your body and can't be forced into your miniature form. But your miniature form serves as a reset should something go wrong with your physical body. Starting off, you automatically have human DNA.