staggered extension process

The staggered extension process (also referred to as StEP) is a common technique used in biotechnology and molecular biology to create new, mutated genes with qualities of one or more initial genes.

The technique itself is a modified polymerase chain reaction with very short (approximately 10 seconds) cycles.

In these cycles the elongation of DNA is very quick (only a few hundred base pairs) and synthesized fragments anneal with complementary fragments of other strands. In this way, mutations of the initial genes are shuffled and in the end genes with new combinations of mutations are amplified.{{cite journal|last=Zhao|first=Huimin |author2=Giver, Lori |author3=Shao, Zhixin |author4=Affholter, Joseph A. |author5=Arnold, Frances H.|title=Molecular evolution by staggered extension process (StEP) in vitro recombination|journal=Nature Biotechnology|year=1998|volume=16|issue=3|pages=258–261|doi=10.1038/nbt0398-258|pmid=9528005 |s2cid=20490024 }}{{cite journal|last=Zhao|first=Huimin|author2=Zha, Wenjuan |title=In vitro 'sexual' evolution through the PCR-based staggered extension process (StEP)|journal=Nature Protocols|date=1 November 2006|volume=1|issue=4|pages=1865–1871|doi=10.1038/nprot.2006.309|pmid=17487170 |s2cid=15317544 }}

The StEP protocol has been found to be useful as a method of directed evolution for the discovery of enzymes useful to industry.{{cite journal|last=Marrs|first=Barry |author2=Delagrave, Simon |author3=Murphy, Dennis|title=Novel approaches for discovering industrial enzymes|journal=Current Opinion in Microbiology|date=29 July 1999|volume=2|issue=3|pages=241–245|doi=10.1016/S1369-5274(99)80042-3|pmid=10383866 }}