You can certainly do this. To select which course elements will impact the final grade of a course;
- click the Manage Courses tab
- click the name of the course you want to edit
- click the Course Element Grading sub-category tab
- select the Override the system defaults for some or all types of course elements radio button
- select the Override the course default for some or all elements radio button
- set your desired override weight for every element within your course
- click the Save button