phosphate group in DNA - (Apr/22/2005 )

Urgent help needed,
Some very basic question,how to calulate the number of phosphate groups in a DNA molecule?For example if I know the size of the plasmid and the concentration/amount of DNA what I used in my experiment is known?

hi
assuming that there is one phosphate group at the 5' termini and that bases are bound by phosphate bound, i would say that there is the same number of phosphate residues as bases of DNA.