primer

A primer is a short single-stranded nucleic acid used by all living organisms in the initiation of DNA synthesis. DNA polymerase (responsible for DNA replication) enzymes are only capable of adding nucleotides to the 3’-end of an existing nucleic acid, requiring a primer be bound to the template before DNA polymerase can begin a complementary strand. Living organisms use solely RNA primers, while laboratory techniques in biochemistry and molecular biology that require in vitro DNA synthesis (such as DNA sequencing and polymerase chain reaction) usually use DNA primers, since they are more temperature stable.

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