Editing Non-coding DNA (section)

===Origins of replication===
{{Main|Origin of replication}}

DNA synthesis begins at specific sites called [[Origin of replication|origins of replication]]. These are regions of the genome where the DNA replication machinery is assembled and the DNA is unwound to begin DNA synthesis. In most cases, replication proceeds in both directions from the replication origin.

The main features of replication origins are sequences where specific initiation proteins are bound. A typical replication origin covers about 100-200 base pairs of DNA. Prokaryotes have one origin of replication per chromosome or plasmid but there are usually multiple origins in eukaryotic chromosomes. The human genome contains about 100,000 origins of replication representing about 0.3% of the genome.<ref>{{cite journal |vauthors=Leonard AC, Méchali M |title=DNA replication origins |journal=Cold Spring Harbor Perspectives in Biology |volume=5 |pages=a010116 |date=2013 |issue=10 |doi=10.1101/cshperspect.a010116|pmid=23838439 |pmc=3783049 }}</ref><ref>{{cite journal |vauthors=Urban JM, Foulk MS, Casella C, Gerbi SA |date=2015 |title=The hunt for origins of DNA replication in multicellular eukaryotes |journal=F1000Prime Reports |volume=7 |page=30 |doi=10.12703/P7-30|pmid=25926981 |pmc=4371235 |doi-access=free }}</ref><ref>{{cite journal |vauthors=Prioleau M, MacAlpine DM |date=2016 |title=DNA replication origins—where do we begin? |journal=Genes & Development |volume=30 |issue=15 |pages=1683–1697 |doi=10.1101/gad.285114.116|pmid=27542827 |pmc=5002974 }}</ref>