Abstract
A flow cytometer produces a DNA distribution which contains information about the proportions of cells in various phases of the cell cycle. The form assumed for the rate of DNA synthesis in a cell plays an important part in the estimation of those proportions. Three forms are compared for the rate of DNA synthesis, one of which is derived from knowledge of the mechanism of DNA replication, and they give substantially different estimates of the proportions of cells in the G1 and g2 + M phases.