Pax6 is a bossy gene — but how exactly does it control what other genes do? The process relies on a few nitty-gritty genetic details:
1. DNA in the cell’s nucleus contains most of the genes in the cell — including the sequence for the Pax6 gene.
2. Genetic information can only leave the nucleus in the form of RNA messages (shown below in red). So in order for a gene to be “turned on,” or expressed, the information it contains is transcribed from the DNA into an RNA message. The same is true for Pax6: to express Pax6, the cell must first create an RNA message that is complementary to the DNA sequence of Pax6.
3. This Pax6 messenger RNA is modified for survival outside the nucleus and then crosses the nuclear membrane into the cell’s cytoplasm.
4. Special cellular structures called ribosomes (shown in tan below) help convert this messenger RNA into a protein (shown in green), in a process known as translation.
5. The protein that Pax6 encodes is called a transcription factor. This sort of protein is particularly powerful. Instead of simply helping build the structure of the cell or carrying on regular cellular processes, transcription factors actually work their way back inside the cell’s nucleus to help direct the expression of other genes.
6. Once inside the nucleus, the Pax6 protein binds to the DNA there and tells other genes to start making proteins and to get to work making an eye!
So Pax6 bosses other genes around by encoding a protein that binds to DNA and turns those other genes on or off. There are other bossy genes involved in eye development and plenty of bossy genes involved in making all of our other organs.