Final answer:
A) Before cell division. DNA replication occurs before cell division to ensure each daughter cell receives an identical copy of the DNA. Without DNA replication or with incomplete replication, genetic abnormalities or malfunctioning cells could occur.
Step-by-step explanation:
DNA replication occurs before cell division.
During the synthesis phase (S phase) of the cell cycle, DNA is copied to form an identical molecule of DNA through a process called DNA replication. This ensures that each daughter cell receives an identical copy of the DNA.
If cell division occurred without DNA replication or with incomplete replication, the daughter cells would not have a complete set of genetic information. This could result in genetic abnormalities or malfunctioning cells.