● In `color{Violet}"living cells"`, such as E. coli, the process of replication requires a `color{Violet}"set of catalysts"` (`color{Violet}"enzymes"`).

● The main enzyme is referred to as `color{Violet}"DNA-dependent"` `color{Violet}"DNA polymerase"`, since it uses a DNA template to catalyse the polymerisation of deoxynucleotides.

● These enzymes are `color{Violet}"highly efficient"` enzymes as they have to `color{Violet}"catalyse polymerisation"` of a large number of nucleotides in a very short time.

● E. coli that has only 4.6 ×`10^6` bp (compared with human whose diploid content is 6.6 × `10^9` bp), completes the process of replication within `color{Violet}"38 minutes"`; that means the average rate of polymerisation has to be approximately `color{Violet}"2000 bp per second"`.

● Not only do these polymerases have to be `color{Violet}"fast"`, but they also have to catalyse the reaction with `color{Violet}"high degree of accuracy"`.

● Any mistake during replication would result into `color{Violet}"mutations"`.

● Furthermore, `color{Violet}"energetically"` replication is a very `color{Violet}"expensive process"`.

● `color{Violet}"Deoxyribonucleoside triphosphates"` serve dual purposes.

● In addition to acting as `color{Violet}"substrates"`, they provide `color{Violet}"energy"` for polymerization reaction (the two `color{Violet}"terminal phosphates"` in a deoxynucleoside triphosphates are `color{Violet}"high-energy phosphates"`, same as in case of `color{Violet}"ATP"`).

● In addition to DNA-dependent DNA polymerases, many `color{Violet}"additional enzymes"` are required to complete the process of replication with `color{Violet}"high degree"` `color{Violet}"of accuracy"`.

● For `color{Violet}"long DNA molecules"`, since the two strands of DNA `color{Violet}"cannot be separated"` in its `color{Violet}"entire length "`(due to very `color{Violet}"high energy"` requirement), the replication occur within a `color{Violet}"small opening"` of the DNA helix, referred to as `color{Violet}"Replication fork"`.

● The DNA-dependent `color{Violet}"DNA polymerases"` catalyse polymerisation only in `color{Violet}"one direction"`, that is `color{Violet}"5'-3' "` .

● This creates some `color{Violet}"additional complications"` at the replicating fork.

● Consequently, on one strand (the template with `color{Violet}"polarity 3'-5' "` ), the replication is `color{Violet}"continuous"`, while on the other (the template with `color{Violet}"polarity 5'-3' "` ), it is `color{Violet}"discontinuous"`.

● The `color{Violet}"discontinuously"` synthesized fragments are later joined by the enzyme `color{Violet}"DNA ligase"`

● The DNA polymerases on their own `color{Violet}"cannot initiate"` the process of replication.

● The replication does not `color{Violet}"initiate randomly"` at any place in DNA.

● There is a `color{Violet}"definite region"` in E. coli DNA where the replication originates.

● Such regions are termed as `color{Violet}"origin of replication"`.

● It is because of the requirement of the `color{Violet}"origin of replication"`, that a piece of DNA, if needed to be propagated during `color{Violet}"recombinant DNA"` procedures, requires a `color{Violet}"vector"`.

● The `color{Violet}"vectors"` provide the origin of replication.

● Further, not every detail of replication is understood well.

● In `color{Violet}"eukaryotes"`, the replication of DNA takes place at `color{Violet}"S-phase"` of the cell-cycle.

● The `color{Violet}"replication"` of DNA and `color{Violet}"cell division"` cycle should be `color{Violet}"highly coordinated"`.

● A `color{Violet}"failure in cell division"` after DNA replication results into `color{Violet}"polyploidy"` (a `color{Violet}"chromosomal anomaly"`).