Deoxyribose is the pentose sugar found in this type of

polynucleotide, hence its name Deoxyribonucleic Acid, or DNA.

The nitrogenous bases found in DNA are, adenine, guanine,

cytosine and thymine. DNA molecules have two polynucleotide 

chains, held together in a ladderlike structure. The sugar phosphate

backbones of the two chains run parallel to each other in opposite

directions. Each "rung" of the ladder is a pair of nitrogenous bases,

one purine and one pyrimidine extending into the center of the

molecule.