General Properties of Cloning Vectors
Cloning vectors are specialized plasmids (or other genetic elements) that will hold any piece of foreign DNA for further study or manipulation. The numbers and types of plasmids available for cloning have grown. In addition, other DNA elements are now used, including viruses and artificial chromosomes. Once a fragment of DNA has been cloned and […]
Radioactive Labeling of Nucleic Acids and Autoradiography
Ultraviolet light absorption is a general method for detecting DNA, but does not distinguish between different DNA molecules. DNA can also be detected with radioactive isotopes During replication, radioactive precursors such as 32P in the form of a phosphate group and 35S in the form of phosphorothioate can be incorporated. Because native DNA does not […]
Restriction Enzymes
The ability to isolate, separate, and visualize DNA fragments would be useless unless some method was available to cut the DNA into fragments of different sizes. In fact, naturally occurring restriction enzymes or restriction endonucleases are the key to making DNA fragments. These bacterial enzymes bind to specific recognition sites on DNA and cut the […]
Gel electrophoresis
Gel electrophoresis followed by staining with ethidium bromide is used to separate DNA fragments by size . The gel of gel electrophoresis consists of agarose , a polysaccharide extracted from seaweed that behaves like gelatin. Agarose is a powder that dissolves in water only when heated. After the solution cools, the agarose hardens. For visualizing […]
DNA Isolation & purification
Basic to all biotechnology research is the ability to manipulate DNA. First and foremost for recombinant DNA work, researchers need a method to isolate DNA from different organisms. Isolating DNA from bacteria is the easiest procedure because bacterial cells have little structure beyond the cell wall and cell membrane. Bacteria such as E. coli are […]
Chi-Square Test
Observed and Expected Ratios: When two individuals of known genotype are crossed, we expect certain ratios of genotypes and phenotypes in the progeny; these expected ratios are based on the Mendelian principles of segregation, independent assortment, and dominance. The ratios of genotypes and phenotypes actually observed among the progeny, however, may deviate from these expectations. […]
Zygomycetes Mucorales
In most members of the Mucorales, numerous spores are contained in globose sporangia borne at the tips of aerial sporangiophores. Within the sporangium the spores may surround a central core or columella, although in some species the columella is greatly reduced. Some species possess fewspored sporangia, termed sporangiola, which are often dispersed as a unit, […]
Taxonomy of fungi
Taxonomy is the science of classification, i.e. the ‘assigning of objects to defined categories’. Classification has three main functions: it provides a framework of recognizable features by which an organism under examination can be identified; it is an attempt to group together organisms that are related to each other; and it assists in the retrieval […]
Cleavage of ascospores
In many ascomycetes, studies of the fine structure of asci during cleavage of the ascospores have shown that a system of double membranes continuous with the endoplasmic reticulum extends from the envelope of the diploid fusion nucleus. The double membrane develops to form a cylindrical envelope lining the young ascus. This peripheral membrane cylinder or […]
Ascus development in Ascomycota
In yeasts and related fungi, the ascus arises directly from a single cell, but in most other ascomycetes it develops from a specialized hypha, the ascogenous hypha, which in turn develops from an ascogonium. Ascogenous hypha The ascogenous hypha of many ascomycetes is multinucleate, and its tip is recurved to form a crozier (shepherd’s crook). […]