A very small number of schools will actually look at your last 45 credits or so. But, it's not the only thing they look at. Usually they want a minimum of XYZ over the last little while, or they will let your overall min gpa be slightly lower if your recent gpa is higher. You'd have to check out each school individually to find out who sets the bar where. Honestly, it's probably not worth much researching, since it only affects whether or not you may apply, not whether or not you'll be favored as an applicant. You will be checking each school's minimum requirements before applying anyway.