Scanning Electron Microscopy Sample Preparation and Imaging.

Scanning electron microscopes allow us to reach magnifications of 20-130,000× and resolve compositional and topographical images with intense detail. These images are created by bombarding a sample with electrons in a focused manner to generate a black and white image from the electrons that bounce off of the sample. The electrons are detected using positively charged detectors. Scanning electron microscopy permits three-dimensional imaging of desiccated specimens or wet cells and tissues by using variable pressure chambers. SEM ultrastructural analysis and intracellular imaging supplement light microscopy for molecular profiling of prokaryotes, plants, and mammals. This chapter demonstrates how to prepare and image samples that are (a) desiccated and conductive, (b) desiccated and nonconductive but coated with an electron conductive film using a gold sputter coater, and

PCR: Identification of Genetic Polymorphisms.

Polymerase chain reaction (PCR) enables the amplification of a specific sequence of deoxyribonucleic acid (DNA) through the process of three main steps: template DNA denaturation, annealing of the primers to complementary sequences, and primer extension to synthesize DNA strands. By using this method, the target sequence will be copied and amplified at an exponential rate. PCR provides a qualitative method for identifying DNA from fresh or dried cells/body fluids, formalin-fixed archival tissue specimens, and ancient specimens.Herein we describe basic information for performing successful PCR experiments using the amplification of a human Alu insertion on the PV92 gene locus on chromosome 16 as an example method.