Beginning of Essay
, or Deoxyribonucleic Acid, is described, in Encarta Encyclopedia as a genetic material of all cellular organisms and most viruses. carries the information needed to direct protein synthesis and replication. Protein synthesis is the production of the proteins nee ....

Middle of Essay
.... the center of the nucleotide, with the phosphate group on one side and a base on the other. The phosphate group of each nucleotide is also linked to the deoxyribose of the adjacent nucleotide in the chain. These linked deoxyribose-phosphate subunits form the side rails of the ladder. The bases face inward toward each other, forming the steps of the ladder. The nucleotides in one strand have a specific association with the corresponding nucleotides in the other strand. Because of the chemical affinity of the bases, nucleotides containing adenine are always paired with nucleotides containing thymine, and nucleotides containing cytosine are always ....