Inside every cell, a complex network of genes determines what it will become — a nerve cell, a muscle cell, or part of the skin. This choice often resembles flipping a toggle switch: two stable positions, and the cell decides which way to tip. But cells have a feature rarely considered in such models: they divide.
The authors took a simple model of a genetic switch and added division to it. They found clear boundaries that separate paths to different fates. It turns out that division can drastically alter these boundaries. Two cells with identical initial settings can end up in opposite states after division. The scientists even identified a region of disagreement — a zone where predictions that ignore division are wrong.
This means that a cell's fate is not always predetermined by its initial state. The very process of division can rewrite the developmental program, creating diversity where it wasn't expected.
The genetic switch studied by the authors works in bacteria in nature, helping them remember environmental conditions and pass this memory on to their offspring.