Editing Genome (section)

== Prokaryotic genomes ==
Prokaryotes and eukaryotes have DNA genomes. Archaea and most bacteria have a single [[circular chromosome]],<ref>{{cite journal |vauthors = Samson RY, Bell SD |title = Archaeal chromosome biology |journal = Journal of Molecular Microbiology and Biotechnology |volume = 24 |issue = 5–6 |pages = 420–27 |date = 2014 |pmid = 25732343 |pmc = 5175462 |doi = 10.1159/000368854 }}</ref> however, some bacterial species have linear or multiple chromosomes.<ref>{{cite book|date=2005|pages=525–540|doi=10.1128/9781555817640.ch29|chapter-url=http://www.asmscience.org/content/book/10.1128/9781555817640.chap29 |last1 = Chaconas |first1 = George |last2 = Chen |first2 = Carton W. |title=The Bacterial Chromosome |chapter=Replication of Linear Bacterial Chromosomes: No Longer Going Around in Circles |name-list-style = vanc |isbn=9781555812324}}</ref><ref>{{cite web|url=http://www.sci.sdsu.edu/~smaloy/MicrobialGenetics/topics/chroms-genes-prots/chromosomes.html|title=Bacterial Chromosomes|website=Microbial Genetics|year=2002}}</ref> If the DNA is replicated faster than the bacterial cells divide, multiple copies of the chromosome can be present in a single cell, and if the cells divide faster than the DNA can be replicated, multiple replication of the chromosome is initiated before the division occurs, allowing daughter cells to inherit complete genomes and already partially replicated chromosomes. Most prokaryotes have very little repetitive DNA in their genomes.<ref name="constraints and plasticity in genome and molecular">{{cite journal |vauthors = Koonin EV, Wolf YI |title = Constraints and plasticity in genome and molecular-phenome evolution |journal = Nature Reviews. Genetics |volume = 11 |issue = 7 |pages = 487–98 |date = July 2010 |pmid = 20548290 |pmc = 3273317 |doi = 10.1038/nrg2810 }}</ref> However, some [[symbiotic bacteria]] (e.g. ''[[Serratia symbiotica]]'') have reduced genomes and a high fraction of pseudogenes: only ~40% of their DNA encodes proteins.<ref>{{cite journal |vauthors = McCutcheon JP, Moran NA |title = Extreme genome reduction in symbiotic bacteria |journal = Nature Reviews. Microbiology |volume = 10 |issue = 1 |pages = 13–26 |date = November 2011 |pmid = 22064560 |doi = 10.1038/nrmicro2670 |s2cid = 7175976 }}</ref><ref>{{cite journal |vauthors = Land M, Hauser L, Jun SR, Nookaew I, Leuze MR, Ahn TH, Karpinets T, Lund O, Kora G, Wassenaar T, Poudel S, Ussery DW |title = Insights from 20 years of bacterial genome sequencing |journal = Functional & Integrative Genomics |volume = 15 |issue = 2 |pages = 141–61 |date = March 2015 |pmid = 25722247 |pmc = 4361730 |doi = 10.1007/s10142-015-0433-4 }}</ref>

Some bacteria have auxiliary genetic material, also part of their genome, which is carried in [[plasmid]]s. For this, the word ''genome'' should not be used as a synonym of ''chromosome''.