MadSci Network: Genetics |
Hi Danielle, While it is true that we cannot see DNA with the naked eye, there are many techniques that can be used to visualize DNA. Electron microscopes can be used to look at DNA on a large scale, i.e. the entire molecule. Chemical techniques allow the precipitation of DNA into viscous solutions readily seen by the naked eye. In addition, there are dyes which can bind to the DNA and glow when light of a particular wavelength shines on it. X-ray crystallography is a technique which solves the structures of molecules mathematically based on a pattern of diffraction generated when x- rays hit a crystal. The molecule of interest has to be "grown" as very small crystals (which can look like quartz under the microscope). X-rays are passed through the crystal and a pattern of diffraction (bending of the rays) is generated on film. Particular structures bend x-rays in different ways. Thus one can identify which structures are present in a particular molecule. The first person to discover the structure of DNA was a scientist named Rosalyn Franklin. She used X-ray crystallography to learn more about the structure of DNA. A double helix (the normal DNA structure) gives a particular pattern of diffraction. Unfortunately, she died at age 38, before the Nobel Prize was given for this discovery. Though she was never recognized for this important discovery, other scientists working on the structure of DNA at the same time used her data to solve the double helix.
Try the links in the MadSci Library for more information on Genetics.