What is the Big Five Model of Personality? What are some of the Leadership traits within the Big Five?

What is the Big Five Model of Personality? What are some of the Leadership traits within the Big Five? Knowing that there is no one list of traits that is accepted by all researchers on what constitutes an effective leader, discuss the following:

Do you agree with this model?

Are there traits that you would classify as less important or more important? Perhaps there is a spectrum? If so, why are some more important than others?
Are there any traits that you would add to the list? Any that you would remove? Why?
Does the importance of a particular trait depend on the situation? How so?
How are these traits related to what we have discussed leadership is?