The formation and breakdown of nucleic acids, such as DNA, involves a crucial process known as dehydration synthesis. This reaction links individual nucleotides together, creating a polymer through the formation of covalent bonds called phosphodiester bonds. These bonds are essential for establishing the sugar-phosphate backbone of the nucleic acid, which exhibits directionality characterized by a 5' end and a 3' end.

The 5' end of the nucleic acid contains a free phosphate group, while the 3' end features a free hydroxyl group. This directional structure is vital for the proper functioning of nucleic acids during processes like replication and transcription. For instance, when two nucleotides, such as cytosine and thymine, are joined through dehydration synthesis, a water molecule is released, and a phosphodiester bond is formed. This results in an alternating sequence of sugar and phosphate groups, creating the sugar-phosphate backbone.

In the context of DNA, the nucleotides involved are specifically deoxyribonucleotides, which lack a hydroxyl group at the 2' position of the sugar, hence the term "deoxy." The nitrogenous bases extend from the sugar-phosphate backbone, contributing to the genetic information encoded within the DNA structure. Understanding these fundamental concepts is essential for grasping the complexities of molecular biology and genetics, as they lay the groundwork for further exploration of nucleic acid functions and interactions.