What type of bond binds the phosphate and sugars in a DNA molecule?

The phosphate group and the pentose sugar (in the case of DNA, deoxyribose) are linked together with a covalent bond, forming the sugar-phosphate backbone of a DNA ladder. The covalent bond is formed when a dehydration synthesis reaction occurs between the (-OH) group coming off of carbon number 3 (on deoxyribose) and the (-OH) group attached to the phosphate group.