5' OH n 3' phosphate groups.....?

In DNA the phosphate is on the 5' of the deoxyribose of the nucleotides and forms a phosphodiesterase bond with the 3' on the deoxyribose of the next nucleotide. As a result each strand of the DNA has a 3'OH end and a 5' phosphate end. DNA grows in the 5' ->3' direction. See diagram in link.