Exogenous DNA
Encyclopedia
Exogenous DNA refers to any deoxyribonucleic acid
that originates outside of the organism of concern or study.
The introduction of exogenous DNA into a cell is called
transfection
. This can take place naturally, as occurs when a virus infects cells, or artificially. Methods of artificial transfection include (a) chemical methods, including calcium phosphate precipitation, DEAE
-dextran complexation and lipid-mediated DNA transfer; (b) physical methods, including electroporation, microinjection, and biolistic particle delivery (gene gun); and (c) using recombinant, lab manipulated viruses as vectors.
The process by which cells take up exogenous DNA from the outside is called transformation
. Bacteria need to be in a certain physiological state to successfully take up exogenous DNA, which is described as one of competence. Some bacteria are naturally competent, but usually only for a brief time at a certain stage of their growth cycle. Bacteria can also be made competent through a variety of chemical treatments including exposure to calcium ions, or a mixture of polyethylene glycol
and dimethylsulfoxide, which make the cell membrane more permeable, leading to the uptake of the exogenous DNA. Another treatment method is the ustilisation of electricity as the membrane-permeabilizing agent (electroporation or electrotransformation). Finally, liposome-mediated transformation can be used. In this method DNA is coated with lipid. Fusion of this lipid and the membrane lipid can occur, facilitating the entry of DNA.
Transformation of bacteria, plant cells and animal cells has important research and commercial functions. Targeted introduction of exogenous DNA is used to identify genes because the introduced DNA can act cause a mutation or altered expression of the gene into which it inserts. This technology, known as insertion mutagenesis, often employs retrovirus
es as the vectors of DNA delivery. Such insertion mutagenesis has been often used to identify many oncogene
s in specific locations in tumor cells.
The use of exogenous DNA to transform cells has spawned the discipline of transgenesis: the use of recombinant DNA techniques to introduce new characters into organisms which were not present previously. The range of organisms that have been created through transgenesis range from bacteria to mammals, including sheep and monkeys, and they have a variety of uses. These include the study of developmental genetics, disease processes and gene regulation
. Transgenic farm animals can produce human pharmaceuticals (a method named pharming), and increased milk or meat production. Tissues and organs from transgenic animals can be used in transfusions and transplants with a lesser chance of immune rejection.
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
that originates outside of the organism of concern or study.
The introduction of exogenous DNA into a cell is called
transfection
Transfection
Transfection is the process of deliberately introducing nucleic acids into cells. The term is used notably for non-viral methods in eukaryotic cells...
. This can take place naturally, as occurs when a virus infects cells, or artificially. Methods of artificial transfection include (a) chemical methods, including calcium phosphate precipitation, DEAE
DEAE
Diethylaminoethyl cellulose is a positively charged resin used in ion exchange chromatography, a type of column chromatography, used in protein and nucleic acid purification/separation...
-dextran complexation and lipid-mediated DNA transfer; (b) physical methods, including electroporation, microinjection, and biolistic particle delivery (gene gun); and (c) using recombinant, lab manipulated viruses as vectors.
The process by which cells take up exogenous DNA from the outside is called transformation
Transformation (genetics)
In molecular biology transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material from its surroundings and taken up through the cell membrane. Transformation occurs naturally in some species of bacteria, but it can...
. Bacteria need to be in a certain physiological state to successfully take up exogenous DNA, which is described as one of competence. Some bacteria are naturally competent, but usually only for a brief time at a certain stage of their growth cycle. Bacteria can also be made competent through a variety of chemical treatments including exposure to calcium ions, or a mixture of polyethylene glycol
Polyethylene glycol
Polyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. It has also been known as polyethylene oxide or polyoxyethylene , depending on its molecular weight, and under the tradename Carbowax.-Available forms:PEG, PEO, or POE refers to an...
and dimethylsulfoxide, which make the cell membrane more permeable, leading to the uptake of the exogenous DNA. Another treatment method is the ustilisation of electricity as the membrane-permeabilizing agent (electroporation or electrotransformation). Finally, liposome-mediated transformation can be used. In this method DNA is coated with lipid. Fusion of this lipid and the membrane lipid can occur, facilitating the entry of DNA.
Transformation of bacteria, plant cells and animal cells has important research and commercial functions. Targeted introduction of exogenous DNA is used to identify genes because the introduced DNA can act cause a mutation or altered expression of the gene into which it inserts. This technology, known as insertion mutagenesis, often employs retrovirus
Retrovirus
A retrovirus is an RNA virus that is duplicated in a host cell using the reverse transcriptase enzyme to produce DNA from its RNA genome. The DNA is then incorporated into the host's genome by an integrase enzyme. The virus thereafter replicates as part of the host cell's DNA...
es as the vectors of DNA delivery. Such insertion mutagenesis has been often used to identify many oncogene
Oncogene
An oncogene is a gene that has the potential to cause cancer. In tumor cells, they are often mutated or expressed at high levels.An oncogene is a gene found in the chromosomes of tumor cells whose activation is associated with the initial and continuing conversion of normal cells into cancer...
s in specific locations in tumor cells.
The use of exogenous DNA to transform cells has spawned the discipline of transgenesis: the use of recombinant DNA techniques to introduce new characters into organisms which were not present previously. The range of organisms that have been created through transgenesis range from bacteria to mammals, including sheep and monkeys, and they have a variety of uses. These include the study of developmental genetics, disease processes and gene regulation
Regulation of gene expression
Gene modulation redirects here. For information on therapeutic regulation of gene expression, see therapeutic gene modulation.Regulation of gene expression includes the processes that cells and viruses use to regulate the way that the information in genes is turned into gene products...
. Transgenic farm animals can produce human pharmaceuticals (a method named pharming), and increased milk or meat production. Tissues and organs from transgenic animals can be used in transfusions and transplants with a lesser chance of immune rejection.