Prokaryotic DNA Replication

When the two strands of dsDNA are separated, each can serve as a template for the replication (synthesis) of a new complementary strand. This produces two daughter molecules, each of which contains two DNA strands (one old, one new) in an antiparallel orientation . This process is called semiconservative replication because, although the parental duplex is separated into two halves (and, therefore, is not conserved as an entity), each of the parental strands remains intact in one of the two new duplexes (Fig. 1).

The enzymes involved in DNA replication are template-directed, magnesium (Mg2⁺)- requiring polymerases that can synthesize the complementary sequence of each strand with extraordinary fidelity. The reactions described in this section were first known from studies of the bacterium Escherichia coli (E. coli), and the description given below refers to the process in prokaryotes. DNA synthesis in higher organisms is more complex but involves the same types of mechanisms.
In either case, initiation of DNA replication commits the cell to continue the process until the entire genome has been replicated.

Figure 1: Semiconservative replication of DNA. T = thymine; A = adenine; C = cytosine; G = guanine.