Here's why:

* DNA replication is the process of copying the entire DNA genome. This is essential because each new cell needs a complete copy of the genetic instructions.

* Cell division is the process by which a single cell divides into two or more daughter cells. This is how organisms grow, repair tissues, and reproduce.

There are two main types of cell division:

* Mitosis: This is the process of creating two identical daughter cells. This is used for growth and repair.

* Meiosis: This is the process of creating four daughter cells with half the number of chromosomes as the parent cell. This is used for sexual reproduction.

In short, DNA replication must happen before cell division can occur so that each new cell receives a complete set of genetic information.