Students fill their chromatographic columns with packing material and separate three colored molecules of known molecular weights as shown in the photograph below. The exercise illustrates how components of a complex mixture can be separated by chromatography and introduces the concept of the standard curve for determining the size of an unknown protein.
2. The Molecular Weight of Hemoglobin
Students determine the size of hemoglobin and estimate the number of amino acid residues in this protein.
This exercise was designed to provide an exciting introduction to specific gene structure and function. In the experiment, students are given two plasmids (A and B) which are identified in the instructors guide. One plasmid (A) has a functional gene for the enzyme ß-galactosidase. The ß-galactosidase gene in the other plasmid (B) is inactive because it contains a segment of foreign DNA. In the first part of the exercise, students analyze restriction digests of both plasmids in order to determine which plasmid should have a functional ß-galactosidase gene.
Locating specific proteins and nucleic acid molecules in tissue sections is an important goal in cell biology. An effective and simple technique for this purpose is tissue printing which permits the localization of specific macromolecules in animal and plant tissues. Here students perform this technique to examine the tissue distribution of the enzyme peroxidase in plants. First, students section carrots, celery, and other vegetables with razor blades and transfer the proteins from the cut sections to nitrocellulose membranes by application of gentle pressure.
Microtubules are hollow cylinders made up of polymers of the protein tubulin. Microtubules are major components of cilia and flagella, which are tail like projections that are covered by a plasma membrane and extend outwards from the cell. Motile cilia are used for locomotion and food gathering by some protozoa and are found in the lining of the trachea, where their wave like motion propels mucus, dust and other foreign matter out of the lungs.
The primary level of chromosome structure in eukaryotes occurs when the DNA molecule is wrapped around histone proteins into particles called nucleosomes. Evidence for this “beads on a string” model is derived from nuclease digestion studies. When nuclei are incubated with micrococcal nuclease, the enzyme cleaves the linker DNA between nucleosomes (the string) but not the nucleosomal core DNA (the beads).
This series of three experiments provides an introduction to agarose gel electrophoresis, In the first experiment, students identify unknown dye molecules by comparing the electrophoresis migration with the migration of known dyes. In the second, they identify dye molecules that bind to DNA and determine the mechanism. They then study four proteins in experiment three and relate differences in they charges to their migration rates in an electric filed.
Recombinant DNA techniques played a central role in the recent emergence of biology into the golden age. This program enables the advanced student to approach these frontiers in biotechnology. The program provides a challenging series of seven 3-hour laboratory sessions which are intended to give students hands-on-experience and a detailed understanding of these new investigative techniques and their potentials.