An oligonucleotide is a short sequence of nucleotides, which are the building blocks of DNA and RNA. Typically consisting of 2 to 50 nucleotides, oligonucleotides can be synthesized in the laboratory and are used in various applications, including genetic research, diagnostics, and therapeutic development. These molecules play a crucial role in techniques such as PCR (polymerase chain reaction) and DNA sequencing. Oligonucleotides can also be designed to bind to specific RNA or DNA sequences, making them valuable tools for gene editing and studying gene expression.