**Luria &
Delbruck Thought Experiment #1 : Induction**

Each of four cultures is started with a
single bacterial cell. Each cell divides once per generation,
producing two cells. At the end of 4 generations, 15
cell divisions produce 2^{4} = 16 cells in each culture, for a total of 64 cells.

In the final generation, each culture
is exposed to the phage. Most bacterial cells are **sensitive
**(**black**). However, ten
cells (3, 1, 5,
& 1 in the four
cultures) are observed to be resistant
(blue). If resistance was **induced** by exposure to bacteriophage,
and all cells have an identical chance of becoming resistant, then
each culture is expected to have an *equal *number of
resistant cells. If the average number of resistant cells per
culture is small, the observed fluctuation among cultures will
follow the **Poisson
Distribution**, for which the variance equals the mean.