DNA polymerase
Molecular Biology · Biochemistry · Biotechnology
Say it: dee-en-AY puh-LIM-uh-rays
DNA polymerase is an enzyme that builds new DNA by adding nucleotides one at a time to a growing strand, using an existing strand as a template.
Also: DNA polymerases, DNA pol
Definition
What is DNA polymerase?
DNA polymerases are the enzymes that make DNA. Each one reads a template strand and attaches the complementary nucleotide (A opposite T, G opposite C) to the free 3' end of a growing strand, so new DNA always lengthens in the 5' to 3' direction. They cannot start a strand from nothing: a short primer, made of RNA in living cells, must supply the first 3' end. The building blocks, deoxynucleoside triphosphates (dNTPs), also supply the energy for each new bond.
Most DNA polymerases also proofread. After adding a base, the enzyme checks the pairing, and if it is wrong, a 3' to 5' exonuclease activity snips it out, which keeps copying errors very rare. Cells have several kinds with different jobs. In E. coli, DNA polymerase III does most of the copying, while DNA polymerase I removes RNA primers and fills the gaps. In eukaryotes, polymerase alpha starts each new stretch, epsilon makes the leading strand and delta the lagging strand; others repair damage or copy mitochondrial DNA.
A heat-stable DNA polymerase from the hot-spring bacterium Thermus aquaticus, Taq polymerase, is the enzyme that drives PCR in the lab.
Word parts
Where does the term “DNA polymerase” come from?
- poly-
- manyGreek polys
- -mer
- partGreek meros
- -ase
- enzymesuffix taken from diastase
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Related
Terms that go with it
- DNA replicationDNA replication is how a cell copies all of its DNA before it divides, so that each daughter cell receives a complete genome.
- Okazaki fragmentAn Okazaki fragment is one of the short pieces of DNA made on the lagging strand during DNA replication and later joined into one continuous strand.
- Polymerase chain reactionThe polymerase chain reaction (PCR) is a lab technique that copies one chosen stretch of DNA over and over until there are billions of copies.
- EnzymeAn enzyme is a biological catalyst, usually a protein, that speeds up a specific chemical reaction without being used up in the process.
- NucleotideA nucleotide is a single unit of DNA or RNA, made of a nitrogen-containing base, a five-carbon sugar and one or more phosphate groups.
- MutationA mutation is a lasting change in an organism's DNA sequence, ranging from a single altered base to large rearrangements of chromosomes.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 14.4 DNA Replication in Prokaryotes
- OpenStax Biology 2e, 14.6 DNA Repair
- NCBI MeSH: DNA-Directed DNA Polymerase
- OpenStax Biology 2e, 17.1 Biotechnology
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