explain how the themes in  dr. jekyll and mr. hyde  are still applicable to students in the 21st century.  

It could be said the the themes are still applicable because the stories deals with some universal themes. For example, " The duality of human nature". This might be contested to students today, because of the choices that they might encounter everyday. every human being decides if he or she wants to be "good" or "evil" , that is to say, taking good or bad decisions that will affect their lives. 
As regards "importance of the reputation", most teens are more concerned about being popular than being a good person or student. It is just a questions of reputation and not a question of being better as humans. 

Hello there! it relates to no dogs barked because both the father and son learn from one another. the theme has to be love as the father misses his child.hope this you! good luck : )