Why there is no member of property for active directory management agent ?

Hi All, 

I am quite new to FIM. I recently look at some videos and blog and Later I search that when we have to add role to user we can not do it directly in user object. Instead we have to add user to group for active directory MA.

I tried to look at list of attribute in Active directory MA Configuration but there is no such property called memberOf. 

Can you please let me know what we have to do manage memberOf attribute in AD.

Thanks.