Replication of DNA is characterised by:

(A) The direction of replication is 5' → 3'.

(B) Only template with 5' → 3' polarity is replicated.

(C) Replication is initiated at ori.

(D) DNA polymerase catalyses the process.

(E) The daughter molecule formed has one parental strand.

Choose the correct answer from the options given below:

(A), (C), (D), (E)

The correct answer is Opttion (3) -(A), (C), (D), (E)

In living cells, such as E. coli, the process of replication requires a set of catalysts (enzymes). The main enzyme is referred to as DNA-dependent DNA polymerase, since it uses a DNA template to catalyse the polymerisation of deoxynucleotides. In addition to DNA-dependent DNA polymerases, many additional enzymes are required to complete the process of replication with high degree of accuracy. For long DNA molecules, since the two strands of DNA cannot be separated in its entire length (due to very high energy requirement), the replication occur within a small opening of the DNA helix, referred to as replication fork. The DNA-dependent DNA polymerases catalyse polymerisation only in one direction, that is 5'→3'. This creates some additional complications at the replicating fork. Consequently, on one strand (the template with polarity 3'→5' ), the replication is continuous, while on the other (the template with polarity 5'→3' ), it is discontinuous. The discontinuously synthesised fragments are later joined by the enzyme DNA ligase. The DNA polymerases on their own cannot initiate the process of replication. Also the replication does not initiate randomly at any place in DNA. There is a definite region in E. coli DNA where the replication originates. Such regions are termed as origin of replication (Ori) . After the completion of replication, each DNA molecule would have one parental and one newly synthesised strand. This scheme was termed as semiconservative DNA replication.