|MadSci Network: Cell Biology|
Dear Katy, Thank you for your question! DNA (deoxyribonucleic acid, a tongue-twister) is like a two-stranded rope that is around 2 nanometers (nm) in diameter. That's three billionths of a meter, or 3x10-9 m. Some comparisons: many atoms are 0.1-0.2 nm in diameter. The common cold virus is a sphere 30 nm across. Brightly colored soap bubbles are about 100-400 nm thick. How long is it? Well, that depends on how much you have. :-) The complete set of genes in each of your cells is 3 billion base pairs. This corresponds to a length of one meter of DNA! Good thing it's so thin, or it wouldn't fit in a cell, let alone the nucleus of the cell. How much does it need to be magnified to be seen with the human eye? Well, most people can see things that are a tenth of a millimeter wide, or 1x10-4 m. So you would need to magnify it at least 1x10-4 ------ = 33,000 times. 3x10-9 You can't do that with an ordinary light microscope. You need a transmission electron microscope or an atomic force microscope to do it. However, you can see DNA in a light microscope if it is balled up into chromosomes, as when a cell divides. Some links for you: DNA Structure [Note: 1 A is 0.1 nm] Atomic force microscopy of DNA How atomic force microscopy works I wasn't able to find a good transmission electron microscope image of DNA on the web. Consult your library for a book on molecular biology. Hope this makes things clearer for you! Deron Walters Rice University
Try the links in the MadSci Library for more information on Cell Biology.