DNA replication occurs in different cellular locations depending on the type of organism:

• In eukaryotic cells , DNA replication takes place in the nucleus , where the cell's chromosomal DNA is housed. This process happens during the S phase of the cell cycle before cell division

• In prokaryotic cells , which lack a nucleus, DNA replication occurs in the nucleoid region , the area within the cell where the circular DNA molecule is located.
• Additionally, in human cells, DNA replication also occurs in the mitochondrial matrix , where mitochondrial DNA is replicated

Thus, DNA replication occurs in the nucleus for eukaryotic chromosomal DNA, in the nucleoid region for prokaryotes, and in mitochondria for mitochondrial DNA in eukaryotic cells.