ABSTRACT
As a note of caution, realize that molecular biology uses a number of noxious chemicals: organic solvents (phenol, chloroform, ether) are quite toxic and certain compounds (ethidium bromide and UV light, for example) are known mutagens capable of causing genetic changes. The use of such compounds has been kept to a minimum in these exercises and where such compounds are used, precautions are noted in directions for the exercises. Nucleic acid samples are often subjected to gel electrophoresis to characterize the size and number of different fragments in the sample. When charged molecules are placed in an electric field, the molecules will migrate towards one of the electrodes, depending on the net charge of the molecule. Nucleic acids have an overall negative charge due to the negative charges associated with the phosphate backbone of the molecules, so they will migrate towards the positive electrode.
