What is the main purpose of the S phase in interphase?

The main purpose of the S phase in interphase is to facilitate the DNA replication process, resulting in the creation of sister chromatids. During this phase, the cell's DNA is accurately duplicated so that each new cell can have an identical copy of the genetic material when the cell divides. This replication is essential for maintaining the integrity of the genetic information across generations of cells.

Effectively, the S phase is a crucial step in the cell cycle, particularly before mitosis, ensuring that each daughter cell receives the correct amount of genetic material. The formation of sister chromatids, which are two identical copies of a chromosome joined together, is vital for the subsequent processes of cell division, allowing for proper segregation of chromosomes into the daughter cells.