So what exactly does this graph actually tell us? Well, we see that at a PH of seven, at a normal PH of seven, all the DNA molecules, 100% of the DNA molecules in the nucleus, exist in their double helix form. Now, as we begin to add a few drops of hydroxide ions, we begin to increase our PH. Now, initially, what happens to our percentage of those molecules that exist in their double helix form? Well, initially the slope is essentially flat. So what that means, the slope is essentially zero.