For example, the DNA in the cells in your toe have the same genes as do the cells in your fingers, eyes, hair, etc… The difference is that the DNA in toe cells, have active toe genes and inactive finger, eye, hair, etc… genes.
What Causes Genes to Be Inactive?
The yellow cord in the diagram represents DNA which is wrapped around protein molecules called histones (the blue cylinders). The colored dot are called epigenomes. The epigenomes are special chemicals that determine the shape of genes. If the epigenome causes the gene to constrict so that it forms a tight coil, then the gene message cannot be read. Thus the gene is inactive.
Remember that a gene is a section of the DNA. In the diagram the epigenomes causes the gene to contract into a tight coil. Let’s pretend this is an inactive finger gene in a toe cell.
In 1978, a teenage boy in North Carolina, went to the doctor because his foot hurt. The doctor found a tooth growing out of the boy’s foot. The problem was solved by pulling the dislocated tooth. Can you explain how this could happen? (The tooth genes in the foot cell were not deactivated.)