Nucleotide

Definition

The monomeric building block of nucleic acids, consisting of a nitrogenous base (purine or pyrimidine), a five-carbon pentose sugar (deoxyribose in DNA, ribose in RNA), and one or more phosphate groups. Nucleotides polymerize via phosphodiester bonds to form DNA and RNA, encode genetic information, and participate in cellular energy transfer (ATP, GTP), signaling (cyclic AMP), and enzymatic reactions. In arthropods, nucleotide variation underlies population genetics, phylogenetic inference, adaptation to environmental stressors, and the evolution of traits such as insecticide resistance or circadian rhythm regulation.

Etymology

From nucleo- (indicating the nucleus, where nucleic acids were first observed) + -ide (chemical suffix denoting a compound)

Example

Comparative analysis of mitochondrial nucleotide substitutions in spider populations has revealed cryptic species boundaries and historical dispersal patterns across fragmented habitats.

Synonyms

• base (loose, in context of sequencing)

Related Terms

• Nucleic acid
• DNA
• RNA
• Genome
• mitochondrial DNA
• Base pair
• Codon
• polymerase chain reaction
• single nucleotide polymorphism

Usage Notes

Distinguished from nucleoside (base plus sugar, lacking phosphate). In molecular systematics, nucleotide characters are the fundamental data for phylogenetic reconstruction; specialists distinguish transitions (purine-purine or pyrimidine-pyrimidine changes) from transversions (purine-pyrimidine changes) when modeling evolutionary rates. The term is often shortened to 'base' in sequencing contexts, though this is imprecise. Plural form refers to multiple monomer units or positions in a sequence; singular refers to one unit or site.