a. Replication of DNA begins at origin of replication site, DNA dependent DNA polymerase helps in polymerisation of deoxynucleotide, replication occurs within a small opening- replication fork , Polymerisation take place in 5’→ 3’ direction only ,one strand grows in continous manner while the other DNA strand grows in discontinuous manner (small stretches) , discontinously synthesised fragments are later joined by the enzyme DNA ligase. b. ‘S’ Phase or synthesis phase in cell cycle is the phase where DNA replication occurs in a cell. If cell division fails to occur after DNA replication in a cell then polyploids will be formed.