click for a larger image

Freshly spooled DNA is very wet and so looks like this.

When the DNA dries out, it practically disappears, like spider web silk.

DNA, The Chemical

During the last stage of isolating genomic (large) DNA, the DNA in water and buffer is made 0.2 M in sodium chloride, NaCl. This helps neutralize the DNA charge along the phosphodiester backbone.

Adding 2 volumes of ethyl alcohol (2 ml of alcohol per ml of DNA-salt solution) makes the solution less polar (charged) and so some of the DNA comes out of solution quickly at the interface of the water and ethanol layers.

The rapid fiber forming DNA traps air bubbles (large bubbles). The DNA fibers begin floating into the ethanol layer, pulling more DNA out of solution.

Spooling onto a glass pipette or stirring rod brings even more DNA out of solution.