What important question remained unanswered by griffith experiment?

Answer 1

Assuming you mean the Frederick Griffith bacterial experiment, the question left unanswered was how the rough strain (less harmful) bacteria transformed into the smooth strain (lethal) bacteria. When he injected live rough strain bacteria, the mouse lived. When he injected live smooth strain bacteria, the mouse died. But if dead smooth strain bacteria was injected, the mouse lived. So if either live rough strain or dead smooth strain could be injected without killing the mouse, then it would stand to reason that one could inject both, the mouse should live. But the mouse died. So he figured the rough strain was somehow taking on the characteristics of the smooth strain bacteria, perhaps by being in close proximity to dead smooth strain bacteria, but he didn't know why. We now know that the smooth strain DNA was somehow getting grafted into the rough strain bacteria and making it able to create a coating which prevented the immune system (of the mouse in this case) from killing it.

In case you mean the John Howard Griffin racial change experiment, the question left unanswered was how to stop racism. While his experiment was not completely successful, he gained a number of insights into the experiences of men of color in America. He was able to speak to people in both groups, but yet, he was not able at that point to get them to reconcile with each other.