Nucleic Acids

Step 1: Understanding the Concept:
Nucleic acids (DNA and RNA) are polymers composed of repeating monomer units called nucleotides. To form the long polymer chain, these individual nucleotides must be chemically linked together.

Step 2: Key Formula or Approach:
Identify the specific functional groups that react to join adjacent nucleotides and the name of the resulting chemical linkage.

Step 3: Detailed Explanation:
A nucleotide consists of three parts: a nitrogenous base, a pentose sugar, and a phosphate group.
In a nucleic acid chain, nucleotides are joined end-to-end. This connection is formed by a condensation reaction between:
1. The hydroxyl ( ) group attached to the carbon of the pentose sugar of one nucleotide.
2. The phosphate group attached to the carbon of the pentose sugar of the adjacent nucleotide.
Because the phosphate group ( ) forms two ester bonds—one with the carbon of its own sugar and a new one with the carbon of the next sugar—the resulting connection bridging the two sugars is called a phosphodiester linkage (or phosphodiester bond).
This linkage forms the continuous "sugar-phosphate backbone" characteristic of all DNA and RNA strands.

Step 4: Final Answer:
The bond is called a phosphodiester bond.