Now, what do we mean by phosphol diaster? So phosphol means we have this phosphate group in between these two aster bonds. So these two bonds are the asterbonds. And that's why we have the dye, because we have these two aster bonds that are linked together by the phosphate group that in turn link together these two sugar molecules in a three to five fashion. So that's what a three prime to five prime phosphodite as the linkage is. So the hydroxyl group on the third carbon of one sugar.