Does your dandruff contain your DNA?
Dear Straight Dope:
I was just watching this science-fiction show where they planned to clone a guy from his dandruff. Does my dandruff really contain my DNA? What the heck is dandruff anyway?
This sounds like a Mystery Science Theatre 3000 movie if there ever was one. Jurassic Park has done much to introduce the public to the frontiers of genetic engineering and biotechnology, even if it stretched things a bit. But why would we want to clone anyone? The Teemings Millions are enough of a handful as it is.
To begin with, virtually EVERY cell in your body contains DNA, that special molecule that contains the plans to build you, an aardvark, or Leif Garrett. The most notable exception is the mature erythrocyte, also known as a red blood cell (immature erythrocytes have a nucleus but lose it upon maturity).
Your skin is formed by layers and layers of cells, much like the pages in a book. Over the course of time, the outermost layers of skin flake off, exposing a new layer underneath. At the bottom, new layers are being created by special cells, thus creating an almost never-ending parade of epithelium. Like red blood cells, epithelial cells contain nuclei in their early stages but not in their later ones. The nucleus is a special compartment in the cell that serves as the control room, which is also where the DNA is housed. Unlike red blood cells, however, the loss of the nucleus in epithelial cells doesn't necessarily mean the loss of DNA. In fact, the deterioration of the nucleus's walls is just that, with the nucleus's contents left intact.
You shed these outermost layers of skin all the time. In fact, a very good portion of household dust is skin cells. Under normal daily activities, they go down the drain when you shower, rub off into your clothes when you work or play, and just plain fly off into the air when you just sit there. However, your hair is an excellent trap for these tiny particles of dead flesh.
So why doesn't EVERYONE have dandruff? Well, to a certain degree, everyone does, but only if you look hard enough--the flakes are usually very small. The condition we call dandruff is different. It can be caused by a fungal infection of the scalp by Pityrosporum ovale, causing the skin cells to shed at a rate much higher than normal. This irritating infection is alleviated by scratching, which causes the skin cells to slough off in huge honkin' flakes. Another cause can be cold, dry weather, which is why some people get itchy scalps during the winter. Regardless of the cause, these flakes contain DNA.
There. I hope that answered your question(s). I think I'm going to go and shower now. Several times.