According to the National Center for Biotechnology Information, the primary role of DNA polymerases is to replicate the DNA of an organism, accurately and efficiently, during cell division. Additionally, polymerases play a vital role in proofreading the genetic code for errors and fixing those that arise.
When an organism begins the process of cellular division, an enzyme called helicase pulls apart the two sides of the DNA molecule. According to Wikipedia, DNA polymerases then start to copy each strand of the original double-stranded DNA. DNA polymerases work directionally: They begin the replication process at the 3’ end of the molecule and work towards the 5’ end of the molecule. However, the newly produced strand is constructed in the opposite direction, thus yielding a complimentary strand to the original.
Wikipedia states that DNA polymerase does not replicate each DNA strand perfectly. On average, the enzyme causes an error in one out of every 1 billion base pairs. However, Nature.com contends that the rate of error is closer to one out of every 1 million base pairs.
The National Center for Biotechnology Information explains that there are many different types of DNA polymerases. Some organisms, such as the ubiquitous bacteria Escherichia coli, have five such polymerases. The organism Saccharomyces cerevisiae uses eight different polymerases, while human beings utilize at least 15 different polymerases.