DNA Replication

DNA Replication is the process by which a DNA molecule produces exact copies of itself, where each of the two parental strands serves as a template for the synthesis of a new complementary strand, resulting in two identical daughter DNA molecules - each containing one parental strand and one newly synthesised strand. This mode is called semi-conservative replication.

Phase: Occurs during the S-phase (Synthesis phase) of interphase in the cell cycle.

DNA replication was first proposed by Watson and Crick in 1953 when they suggested that the specific base pairing in the double helix "immediately suggests a possible copying mechanism for the genetic material." The process was experimentally confirmed as semi-conservative by Meselson and Stahl (1958) in E. coli.

Replication is essential because every cell that divides must pass an identical copy of the genome to each daughter cell. The process is highly accurate - even a single error results in a mutation.

Before Meselson and Stahl's experiment, three models were proposed:​

The process by which DNA duplicates itself is called replication. 

When DNA directs the synthesis of chemical molecules other than itself, then such functions of DNA are called heterocatalytic functions. Eg, Synthesis of RNA (transcription), synthesis of protein (Translation), etc.

When DNA directs the synthesis of DNA itself, then such function of DNA is called autocatalytic function. Eg. Replication.

• DNA replication is the process by which a DNA molecule makes exact copies of itself, each parental strand acting as a template for a new complementary strand, giving two identical daughter molecules with one old and one new strand each (semi-conservative).
• It occurs during the S-phase (Synthesis phase) of interphase in the cell cycle.
• Proposed by Watson and Crick (1953) and experimentally confirmed as semi-conservative by Meselson and Stahl (1958) in E. coli.
• Of the three proposed models, semi-conservative was proved correct, while conservative and dispersive were disproved.
• Replication is an autocatalytic function (DNA making DNA), unlike heterocatalytic functions, where DNA directs the synthesis of other molecules, like RNA (transcription) or protein (translation).