When single-celled organisms are first introduced to a liquid culture, they show little growth at first, as it takes time for them to respond to the nutrient rich environment. This is referred to as lag phase. Following this, the organism will grow rapidly following a logarithmic growth pattern, referred to as log phase or exponential phase. Finally, the organism will saturate the media and cease to grow. This is referred to as stationary phase.
In this diagram, lag phase is marked by the number 1, log phase by the number 2, and stationary phase by the number 3.
Using mutagens to induce mutations in model organisms is a common and important laboratory technique. When mutagenizing single-celled organisms, the mutagens are typically administered during the log phase.
Because mutagens are used to induce changes in the organism's DNA, which of the following is the MOST important reason for adding mutagens during log phase?