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Electroporation
Course: Cell Biology (BIO 108 )
44 Documents
Students shared 44 documents in this course
University: Long Island University
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ELECTROPORATION
It consists of applying short high voltage pulses to a mixture of host cells
in suspension and recombinant vectors in solution. These pulses increase the permeability
of the membranes, allowing the vectors to pass into the cell.
It is a highly efficient method that can be applied to all types of host cells.
Selection and identification of recombinant clones
Once the vector introduction process is finished, a mixture with
three types of cells is obtained:
- Non-transformed cells, which have not captured any DNA molecule.
- Transformed cells that carry the recombinant vector.
- Transformed cells that carry a non-recombinant vector or somemolecule
unwanted DNA.
Therefore, a process of selection and identification of theclones is necessary
recombinant, which will be those that carry the specific recombinant vector.
This selection process is conditioned by genetic markers carried by the
vector: antibiotic resistance genes, enzymes that produce colored reactions,
fluorescent proteins, lethal genes, etc.
It is one of the first selection and identification systems and is based on the use of
vectors with two antibiotic resistance genes, usually ampicillin and tetracycline.
The insertion site of the foreign DNA is inside the sequence of one
of the resistance genes, so that in recombinant vectors that gene is not
functional (its sequence is interrupted by the insert of foreign DNA).
When this vector is introduced into bacteria sensitive to ampicillin and tetracycline,are
three types of cellsobtained:
- Cells not transformed with the vector: sensitive to both antibiotics.
- Cells transformed with the recombinant vector: resistant to ampicillin and
sensitive to tetracycline.
- Cells transformed with the non-recombinant vector: resistant to both
antibiotics.
With this system, selection is carried out by cultivating the cells in a culture medium with
ampicillin in which only the transformed bacteria will grow. Identification is done by
replicating the ampicillin plate on another tetracycline plate. Consequently, the recombinant
clones will be the colonies that grow on the ampicillin plate and do not grow on the one
containing tetracycline.
Fluorescent proteins
It is based on the use of vectors with a resistance gene for selection and
a gene encoding a fluorescent protein for identification. The polylinker region is included
in the fluorescent protein gene, so the inserts inactivate the gene. The most widely used
protein is GFP, isolated from a jellyfish.