However, the simplicity of this idea may lead to misinterpretations in some circumstances. The growth rate of a population may be reduced if the length of the cell cycle increases. However, the growth rate may also be reduced if only a fraction of the cells are dividing. Using equations to model growing populations of cells requires knowledge about the cells themselves. This is particularly important when modelling the growth of cancerous cells.
Many cells die quickly, leaving only a fraction of cancerous cells dividing.
When modelling the growth of a population of cells, it is commonly useful to assume that every individual cell doubles with every cell cycle, i.e. the daughter cells themselves divide upon completion of the next cell cycle. This is typically expressed as an exponentially or geometrically growing population. By varying f, we can see how the rate of growth affects the growth of the population. Alternatively, it may be the result of a reduction in the fraction of cells that are dividing. Since the exponential equation assumes all cells divide, we may be misinterpreting the graphs by assuming a reduction in the length of the cell cycle.