|MadSci Network: Molecular Biology|
Hi Dean! Forgive my asking, but aren't you a little young to be worried about the future of your nucleic acids? You are correct that our DNA suffers cumulative and irreversible damage over time. For instance, the telomeres which form the "ends" of each linear, double-helical human chromosome get smaller with each cell division. Some models of aging have suggested that telomere shortening acts as an intrinsic clock for cells; after a certain number of divisions, the cells die. Exposure to environmental factors, including UV light or free radicals, can also alter DNA. Getting DNA out of cells isn't too difficult. Basically, you need to lyse the cells, remove the carbohydrates/lipids/proteins/RNA, and isolate the remaining DNA. You can extract bacterial DNA by lysing the cells in an alkaline-detergent solution, then using centrifugation and various solvents to get rid of proteins. RNA is removed by treating with RNase enzymes. For mammalian cells, the problem is a little trickier -- the chromosomes are long, so you want to treat the DNA gently to avoid shearing. Many biotech/ chemical companies sell kits which make it easy to extract pure, unscathed human DNA, or you can use the simple techniques referenced below. Here's the rub: while in principle you only need a few cells to get sufficient DNA for certain molecular biology techniques, in practice it takes a lot of cells to get a visible speck of DNA. For bacteria, you can grow oodles of cells in just 1 mL of medium, so that's not a problem. For human cells, blood (maybe 10 mL or so) is the preferred source. A GP should be able to draw blood in her office quickly and (more or less) painlessly, using appropriate techniques. Only a subset of the cells contained in blood will be useful for your purposes, since red blood cells do not contain nuclei. Centrifugation is the preferred method of separating white cells from the rest of the blood. I would not advise any invasive surgical procedures to acquire stem cells and the like -- really, you need not have your GP mining for bone marrow or liver. If you're afraid of needles, I suppose you could scrape epithelial cells from the inside of your cheek and culture them, but contamination with all the nasty bacteria that live inside our mouths would be a potential problem. As for storage, DNA stores well in a buffered solution (like TRIS-EDTA) at -20 C (a standard freezer temperature). No liquid nitrogen necessary. Here's a smorgasbord of DNA extraction tips (how to extract DNA from human cells, bacteria, lice, and so forth ....): http://hdklab.wustl.edu/lab_manual/dna/dna1.html Hope this helps, and have fun! Amanda Kahn firstname.lastname@example.org
Try the links in the MadSci Library for more information on Molecular Biology.