The Antimetabolites

Antimetabolites are synthetic metabolites designed to mimic those naturally produced by the body.

These agents replace the purines, pyrimidines, or folates required for the metabolic synthesis of nucleic acids and DNA.

They exert their effect during the S phase of the cell life cycle and are subdivided into folate, purine and pyrimidine antagonists.

The M Phase

M = Mitosis

During the M phase, the cell undergoes cell division. Cell division consists of nuclear division (mitosis) and cytoplasmic division (cytokinesis). The M phase ends on completion of cell division.

Nuclear Division: At the start of the M phase, the cell contains double the amount of nuclear DNA and the chromosomes each consist of two sister chromatids. During mitosis, the cell divides into two daughter cells and one chromatid from each chromosome goes into each daughter cell.

The G₂ Phase

G = Growth

The G₂ phase is the later growth phase.

The S Phase

The S phase is the phase in which DNA is synthesised. The phase starts when DNA synthesis starts and ends when the amount of nuclear DNA has doubled and the chromosomes have replicated. At the end of the S phase, each chromosome will consist of two sister chromatids.

The G₁ Phase

G = Growth

The G₁ phase is the early growth phase. During mitosis, biosynthetic activities of the cell become very slow. In the G₁ phase, these activities resume at a high rate.

The G₀ Phase

G = Growth

A newly divided cell may re-enter the cell cycle, or it may enter the G₀ phase which is a resting, non-proliferative phase.