You are a researcher in the Plant Biodiversity Department. Three types of mango leave isolated from Gunung Ledang, Lembah Pantai and Kota Bharu were sent to your department/laboratory. Suggest the most appropriate method to study the expression levels of steroid-related genes (steroid gene A, steroid gene B, and steroid gene C) in all of the samples. Justify why the suggested method is the best approach.