We present 3D hydrodynamic simulations aimed at studying the dynamical and chemical evolution of the interstellar medium in dwarf spheroidal galaxies .
This evolution is driven by the explosions of Type II and Type Ia supernovae , whose different contribution is explicitly taken into account in our models .
We compare our results with avaiable properties of the Draco galaxy .
Despite the huge amount of energy released by SNe explosions , in our model the galaxy is able to retain most of the gas allowing a long period ( > 3 Gyr ) of star formation , consistent with the star formation history derived by observations .
The stellar [ Fe/H ] distribution found in our model matches very well the observed one .
The chemical properties of the stars derive from the different temporal evolution between Type Ia and Type II supernova rate , and from the different mixing of the metals produced by the two types of supernovae .
We reproduce successfully the observed [ O/Fe ] - [ Fe/H ] diagram .