Editing DNA synthesis (section)

==Polymerase chain reaction==
[[File:Polymerase chain reaction-en.svg|upright=1.25|thumb|right]]
A [[polymerase chain reaction]] is a form of enzymatic DNA synthesis in the laboratory, using cycles of repeated heating and cooling of the reaction for [[DNA melting]] and enzymatic replication of the DNA.

DNA synthesis during PCR is very similar to living cells but has very specific reagents and conditions. During PCR, DNA is chemically extracted from host chaperone proteins then heated, causing thermal dissociation of the DNA strands. Two new cDNA strands are built from the original strand, these strands can be split again to act as the template for further PCR products. The original DNA is multiplied through many rounds of PCR.<ref name=Pelt-Verkuil/>  More than a billion copies of the original DNA strand can be made.

===Random mutagenesis===
For many experiments, such as structural and evolutionary studies, scientists need to produce a large library of variants of a particular DNA sequence. Random mutagenesis takes place in vitro, when mutagenic replication with a low fidelity DNA polymerase is combined with selective PCR amplification to produce many copies of mutant DNA.<ref>{{cite journal |last1=Forloni |first1=M |title=Random Mutagenesis Using Error-prone DNA Polymerases. |journal=Cold Spring Harbor Protocols |date=2018 |volume=2018 |issue=3 |pages=pdb.prot097741 |doi=10.1101/pdb.prot097741|pmid=29496818 }}</ref>

===RT-PCR===
RT-PCR differs from conventional PCR as it synthesizes cDNA from mRNA, rather than template DNA. The technique couples a reverse transcription reaction with PCR-based amplification, as an RNA sequence acts as a template for the enzyme, reverse transcriptase. RT-PCR is often used to test gene expression in particular tissue or cell types at various developmental stages or to test for genetic disorders.<ref>{{cite book |last1=Bachman |first1=Julia |title=Chapter Two - Reverse-Transcription PCR (RT-PCR) |series=Methods in Enzymology |date=2013 |volume=530 |pages=67–74 |doi=10.1016/B978-0-12-420037-1.00002-6 |pmid=24034314 |url=https://www.sciencedirect.com/science/article/pii/B9780124200371000026}}</ref>