Nucleotide base

Chemical compounds that are the building blocks of DNA and RNA

Diagram showing the nucleotide bases in DNA and RNA.

Nucleotide bases, also known as nitrogenous bases, are the fundamental building blocks of nucleic acids, which include DNA and RNA. These bases are crucial for the storage and expression of genetic information in all living organisms. There are two main categories of nucleotide bases: purines and pyrimidines.

Structure

Nucleotide bases are organic molecules that contain nitrogen atoms. They are classified into two types based on their structure:

Purines

Diagram of purine bases: adenine and guanine.

Purines are larger, double-ring structures composed of a six-membered and a five-membered nitrogen-containing ring, fused together. The two primary purines found in nucleic acids are adenine (A) and guanine (G). These bases pair with specific pyrimidines to form the rungs of the DNA double helix.

Pyrimidines

Diagram of pyrimidine bases: cytosine, thymine, and uracil.

Pyrimidines are smaller, single-ring structures. The main pyrimidines in DNA are cytosine (C) and thymine (T), while in RNA, thymine is replaced by uracil (U). These bases pair with purines to maintain the structure of nucleic acids.

Function

Nucleotide bases play a critical role in the storage and transmission of genetic information. In DNA, the sequence of bases encodes the genetic instructions used in the development and functioning of living organisms. During DNA replication, these bases pair specifically (adenine with thymine, and guanine with cytosine) to ensure accurate copying of genetic information.

In RNA, nucleotide bases are involved in protein synthesis. The sequence of bases in messenger RNA (mRNA) is translated into a sequence of amino acids, forming proteins that perform various functions in the cell.

Modified Bases

In addition to the standard bases, there are several modified bases that occur naturally in nucleic acids. These modifications can affect the structure and function of nucleic acids.

Hypoxanthine and Xanthine

Structure of hypoxanthine.

Structure of xanthine.

Hypoxanthine and xanthine are purine derivatives that can be found in tRNA and are involved in various metabolic pathways.

7-Methylguanine and 7-Methylguanosine

Structure of 7-methylguanine.

Structure of 7-methylguanosine.

These are methylated forms of guanine that play roles in the regulation of gene expression and RNA stability.

Inosine and Xanthosine

Structure of inosine.

Structure of xanthosine.

Inosine is found in tRNA and is important for the wobble base pairing, allowing for flexibility in the genetic code. Xanthosine is a nucleoside that can be involved in various biochemical processes.

Related Pages

• DNA
• RNA
• Nucleic acid
• Base pair
• Genetic code