I spent some time looking for an explanation of what makes chimera African violets different from the the other African violets. Either the explanation was over simplified to the point it was misleading and frankly provided no real explanation or were so complicated two paragraphs into the dissertation my eyes glazed over. So my goal was to find an explanation that was satisfying yet understandable. After searching the web for sometime I think one of the best explanations was found on the http://aggie-horticulture.tamu.edu/violet/violet.html and a few others listed below. I took parts and pieces from the few best explanations and put the below explanation together.
So where do chimera African violets come from? How does it all start? Chimeras arise when one cell in the plant in a special area of the plant (near the top of the apical dome) undergoes a mutation. That mutation can just be spontaneous or it may be purposefully induced by chemicals or irradiation. If a cell mutates and it is located near the top of the apical dome (see the illustration below that shows the mutated cell), then all other cells which are produced from that mutated cell by division from it, will also be of the mutated cell type. What you then have are two genetically different cells residing together to make up the plant.
A question you may now have is OK, but what is apical dome? And where is it? Apical dome is actually found in two locations on a plant, the root and the stem. It is where the active growing site of the stem and roots occurs. When we refer to the apical dome we can use a more common term of apical meristems. The dome is made up of meristem cells. These are cells that can become anything. They are referred to as being undifferentiated. They can become branches, leaves and flowers. The main function of the apical meristems is to begin growth of new cells in young seedlings or at the tips of roots and shoots. A active growing apical meristem lays down a growing root or shoot behind itself, and continues to grow pushing itself forward. T chimera effect we see in African violets is the result of a mutation in the shoot apical meristems.
So how does this tie into chimera African violet pinwheel flowers? Chimera African violets are produced when the mutated cell (remember they are two different populations of cells, mutated and normal growing together) do not entirely cover the apical dome. A mutated cell layer exists on only a portion of the meristem. See the 3rd image above. As a result you get the “pinwheel flowering” effect.
There is a lot more to all of this but this is the most basic explanation that I hope was not too simple and provided enough meat to either satisfy or if you want more the web has it and you can get into the three types of plant chimer-isms.
1) Image used above
Click to take you to the source of the image
2) sources of information