The researchers compare the DNA to a childhood slinky toy. The researchers compared coiled DNA in brain neurons to a slinky toy – which can be affected by stress. The researchers found that stress on the mice increased the abundance of an enzyme called SETD7. More SETD7 led to more chemical tags designated as H3K4me1 – chemical tags that label DNA as ready for uncoiling inside the VTA neurons. What that essentially does is make it easier for genes in these dopamine-producing cells to be turned on in the future.