Relative pronouns are used to create balance among clauses by connecting them together. In the sentence: The game was designed by Zack, who studies computer programming. "Who" is the relative pronoun and connects the clauses "the game was designed" and "studies computer programming". You will see that even though the second clause is called a clause, no subject is present. That is because "who" stands in the position of being a subject. Therefore, "who studies computer programming" becomes a complete clause.