The stiffness of DNA, quantified by the persistence length, is a property that dictates much of the conformational forms and behavior of the molecule. At the moment it is not clear how the persistence length changes along the molecule due to base pair sequence or external effects like temperature. We aim to shed some light in the matter by recording SANS curves of a couple of known short chain sequences during the melting transition or thermal denaturation of DNA. From the SANS curves we expect to infer the radius of gyration of the molecules and then relate it to the persistence length through theory models. Comparing these results for both sequences and the different temperatures one could imply what are the effects of base pair sequence and temperature in this important parameter of the DNA.