This animation shows how varying concentrations of a signaling molecule activate different transcription factors to determine cell fate.

Signaling molecules, such as secreted proteins, can form chemical gradients along an area of the body. As shown in the animation, cells along the gradient are exposed to different concentrations of the signaling molecule. These varying concentrations activate different levels of transcription factors, changing how the cells differentiate. Processes like these play important roles in helping body parts and organs develop, depending on their positions in the body.

This animation is a clip from a 2008 Holiday Lecture Series, Making Your Mind: Molecules, Motion, and Memory. Depending on students’ background, it may be helpful to pause the animation at various points to discuss different steps in the process.