a) Explain the process of DNA replication with the help of a schematic diagram.
b) In which phase of the cell cycle does replication occur in Eukaryotes? What would happen if cell-division is not followed after DNA replication?

Explanation

a) DNA replication is the pheonmen in which a duplicate copy of DNA is synthesised. The steps involved in the process of DNA replication are as follows:
i) DNA replication occurs in S-phase of the cellcyle.
ii) Enzyme involved: DNA polymerase (DNA dependent DNA polymerase)
iii) Replication requires energy. Source of energy "Deoxyribonucleoside triphosphates (DNTPs)
iv) DNTPs have dual purpose: act as substrates as well as provide energy.
v) Replication initiates at specific regions in DNA called the origin of replication.
vi) DNA polymerase polymerises a large number of nucleotides in a very short time.
vii) During the course of replication, two parent strans do not completely open, but a small opening forms in which replication occurs. This small opening forms a replication fork.
viii) DNA polymerase can polymerise only in one direction.
xiv) Therefore, replication occurs smoothly at one end of DNA (continuous replication but occurs discontinuously at the other end).
xv) The discontinous fragments so formed are joined by DNA ligase.
b) DNA replication occurs in S phase of cell cycle in eukaryotes.
If cell division is not followed after DNA replication then the replicated chromosomes (DNA) would not be distributed to daughter nuclei resulting in polyploidy (a chromosome anomaly).