A lifetime ban from the zoo.
Explanation: This joke implies that mixing human DNA with elephant DNA suggests a scenario where a human might copulate with an elephant, which is absurd and humorous. The punchline, “a lifetime ban from the zoo,” suggests that engaging in such an inappropriate act would lead to severe consequences, such as being banned from the zoo. The humor relies on the shocking imagery and the exaggerated implication of the situation, creating a funny and unexpected twist.