Nucleotide sequence databases are organized collections of biological data that store sequences of nucleotides, the building blocks of DNA and RNA. These databases allow researchers to access, analyze, and compare genetic information from various organisms, facilitating studies in genetics, evolution, and molecular biology. Examples of such databases include GenBank, EMBL, and DDBJ. These databases typically provide tools for searching and retrieving sequences, along with annotations that describe the function and origin of the sequences. They play a crucial role in bioinformatics, enabling scientists to share and collaborate on genetic research, ultimately advancing our understanding of life at the molecular level.