Students isolate nuclei from calf thymus tissue and examine them microscopically. The DNA is then extracted from the nuclei by a simple procedure that uses a detergent and alcohol. Microscopes and a small centrifuge are desirable but not absolutely necessary for the exercise.
Cell respiration can be viewed as a series of enzyme catalyzed reactions in which carbohydrates, proteins, and fats are broken down to carbon dioxide and water with the release of energy. During the process, hydrogen is removed from the fuel molecules and oxygen is consumed. With this background information, students measure oxygen consumption and hydrogen liberation in germinating barley at different temperatures. The program provides eight calibrated respirometers for measurement of oxygen consumption and the chemicals required to perform a graphic dye reduction assay.
Acid phosphatase is present in many plant tissues where it catalyzes the removal of phosphate groups from macromolecules at low pH. In this exercise, students prepare a cell-free extract from wheat germ and determine the amount of the enzyme present in the extract. The experiment offers practical experience with enzyme extraction procedures and is an excellent introduction to the analysis of enzyme activity and basic enzyme kinetics.
A colorimeter is desirable but not absolutely necessary for this exercise.
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.
Students are introduced to the theory of separating proteins according to charge differences using electrophoresis. They then study four proteins and relate differences in their charges to their migration rates in an electric field. Each protein is a different color so that its progress during the separation can easily be followed.
Many changes in the structure of hemoglobin have arisen by mutations. About one person in 100 carries a mutant hemoglobin gene, and these individuals have abnormal hemoglobin molecules in their blood. One of the most common abnormal hemoglobins is hemoglobin S, which causes sickle cell anemia. When the gene for hemoglobin S is inherited from both parents, all of the hemoglobin in the circulation is hemoglobin S and the individual suffers from severe anemia.
Electrophoresis in agarose gels is the most common method used for determining the size of DNA molecules. In this introductory exercise, students determine the length of an unknown DNA molecule by comparing its electrophoretic mobility with six DNA molecules of known size as shown.
Bacteriophage lambda is a DNA virus that attacks E. coli. Here, students dissect lambda DNA using the restriction endonucleases EcoR1 and BamH1 in order to identify specific sites, sequences, and structures along the phage genome. This single exercise enables students to explore a number of exciting topics in molecular biology, including the specificity of restriction endonucleases, DNA mapping strategies, complementary base-pairing of DNA, and the structure of a viral genome.
Chemical signaling between cells in multicellular organisms is frequently mediated by cell-surface receptors. The receptors for neurotransmitters, protein hormones, growth factors, and plant lectins are a few of the many known examples of these important membrane components. In this exercise, students examine the cell location and properties of the receptor for the lectin concanavalin A. In the first experiment of the series, students use a concanavalin A-peroxidase complex in a microscopic assay to show that the specific receptor is found on the surface of their own cheek epithelial cells.
Satellite DNAs are highly repeated sequences of unknown function. The satellite DNA from the meal worm beetle is remarkable since it represents over 50% of this insects genome. In this exercise, students first isolate DNA from beetle larvae by a simple and safe procedure. They then digest the DNA with EcoR1 and examine the satellite DNA following electrophoresis as shown on the gel pictured below. Suffient materials are provided so that the experiment can be carried out twice by eight groups of students.
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.
This program was designed to actively engage students in exciting biological research projects of their own design. The projects focus on peroxidases, which form a large family of related enzymes that are ubiquitous in plants. Plant peroxidase isoenzymes can be tissue specific, developmentally regulated and display variable tissue and, high salt and disease resistance defense reactions and this induction may be related to the abilities of peroxidases to strengthen the plant cell wall and to kill microorganisms.
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.
A mutation is a change in the nucleotide sequence of DNA which leads to an inherited change in an organism. Restriction endonucleases provide valuable tools for characterizing mutations at the DNA level. This principle is illustrated in the exercise where students digest a normal and a mutant gene with EcoR1 and Hae III and then analyze the DNA fragments from each by electrophoresis as shown in the figure below. The gene is from rabbit and codes for the ß-globin chains of hemoglobin.
The emission of light by living organisms is a fascinating process. The genetic system required for luminescence in the bacterium Photobacterium (Vibiro) fischeri is the lux operon. This operon contains a gene for luciferase (the enzyme that catalyzes the light-emitting reaction) and genes for enzymes which produce the luciferins (which are the substrates for the light-emitting reaction.). In this exercise, students create a luminescent population of bacteria by introducing into E.coli a plasmid that contains this lux operon.