All nucleotides contain a pentose (5C) sugar, a phosphate group and a nitrogen containing base. In the case of a DNA nucleotide the nitrogen containing bases can be adenine, guanine, cytosine and thymine and it contains the pentose sugar deoxyribose. In an RNA nucleotide the nitrogen containing bases are adenine, guanine, cytosine and uracil (replacing thymine from the DNA) and RNA contains the pentose sugar ribose.