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Introduction to Transformation
In this lab, your students will perform a procedure known as genetic transformation.
Genetic transformation occurs when a cell takes up (takes inside) and expresses a new
piece of genetic material—DNA. This new genetic information often provides the organism
with a new trait which is identifiable after transformation. Genetic transformation literally
means change caused by genes and involves the insertion of one or more gene(s) into an
organism in order to change the organism’s traits.
Genetic transformation is used in many areas of biotechnology. In agriculture, genes coding
for traits such as frost, pest, or drought resistance can be genetically transformed into
plants. In bioremediation, bacteria can be genetically transformed with genes enabling
them to digest oil spills. In medicine, diseases caused by defective genes are beginning to
be treated by gene therapy; that is, by genetically transforming a sick person’s cells with
healthy copies of the defective gene that causes their disease.
Genes can be cut out of human, animal, or plant DNA and placed inside bacteria. For example,
a healthy human gene for the hormone insulin can be put into bacteria. Under the right conditions,
these bacteria can make authentic human insulin. This insulin can then be used to treat
patients with the genetic disease, diabetes, because their insulin genes do not function normally.
The pGLO System
With the pGLO transformation kit, students use a simple procedure to transform bacteria
with a gene that codes for Green Fluorescent Protein (GFP). The real-life source of this
gene is the bioluminescent jellyfish
Aequorea victoria
, and GFP causes the jellyfish to
fluoresce and glow in the dark. Following the transformation procedure, the bacteria
express their newly acquired jellyfish gene and produce the fluorescent protein which causes
them to glow a brilliant green color under ultraviolet light.
In this activity, students will learn about the process of moving genes from one organism
to another with the aid of a plasmid. In addition to one large chromosome, bacteria naturally
contain one or more small circular pieces of DNA called plasmids. Plasmid DNA usually
contains genes for one or more traits that may be beneficial to bacterial survival. In nature,
bacteria can transfer plasmids back and forth, allowing them to share these beneficial
genes. This natural mechanism allows bacteria to adapt to new environments. The recent
occurrence of bacterial resistance to antibiotics is due to the transmission of plasmids.
Bio-Rad’s unique pGLO plasmid contains the gene for GFP and a gene for resistance to the
antibiotic ampicillin. pGLO also incorporates a special gene regulation system that can be used
to control expression of the fluorescent protein in transformed cells. The gene for GFPcan be
switched on in transformedcells simply by adding the sugar arabinoseto the cell’s nutrient
medium. Selection for cells that have been transformed with pGLO DNA is accomplished by
growth on antibiotic plates. Transformed cells will appear white (wild-type phenotype) on plates
not containing arabinose, and fluorescent green when arabinose is included in the nutrient agar.
The unique construction of pGLO allows educators and students, for the very first time, to easily
explore mechanisms of gene regulation (Appendix D) and genetic selection. And, the entire
process is observable with an inexpensive long-wave UV lamp or with the provided pen-light.
In order for your students to gain the most from this experiment, they should know what
a gene is and understand the relationship between genes and proteins. For a more
detailed discussion of these and other basic molecular biology concepts and terms, refer to
the review provided in Appendix B.
This pGLO transformation kit provides the opportunity for additional activities involving
purification of the recombinant fluorescent protein from transformed bacteria using the GFP
chromatography kit (catalog # 166-0005EDU) and the separation of proteins expressed in
E. coli
, such as the GFP protein by using the pGLO SDS-PAGE Extension kit (catalog
#166-0013EDU.)
