A pathogenic bacterium of plants that can inject a plasmid DNA (T DNA) into plant cells.
One of the variant forms of a gene at a particular locus, or location, on a chromosome. Different alleles produce variation in inherited characteristics such as blood type. In an individual, the dominant form of the allele might be expressed more than the recessive one.
Transplantation of cells, tissues, or organs from another member of the same species.
Transgenic animals modified to produce proteins for extraction, purification, and therapeutic use.
The production of biopharmaceuticals in domestic animals.
Measures to protect from infection.
Bovine spongiform encephalopathy (BSE)
A disease of cattle, related to scrapie of sheep, also know as “mad cow disease.” It is hypothesized to be caused by a prion, or small protein, which alters the structure of a normal brain protein, resulting in destruction of brain neural tissue.
Animals (or embryos) composed of cells of different genetic origin.
Defines both molecular clones and whole-animal clones.
The propagation of genetically exact duplicates of an organism by a means other than sexual reproduction; for example, the vegetative production of new plants or the propagation of DNA molecules by insertion into plasmids. Often, but inaccurately, used to refer to the propagation of animals by nuclear transfer.
Growth of cultured cells together.
Living on or within another organism, and deriving benefit without harming the host.
DNA sequences in genes that interact with regulatory proteins (such as transcription factors) to determine the rate and timing of expression of the genes as well as the beginning and end of the transcript.
A heritable chemical modification of DNA (replacement of cytosine by 5-methyl cytosine) that, when present in a control region, usually suppresses expression of the corresponding gene.
CJD or Creutzfeldt-Jakob Disease
A disease of humans hypothesized to be caused by a prion, or small protein, which alters the structure of a normal brain protein, resulting in destruction of brain neural tissue. The most common form is thought to have genetic origins. There is strong epidemiologic and laboratory evidence for a causal association between new variant CJD and BSE.
A common, usually benign, herpesvirus that can cause life-threatening infection in immunosuppressed individuals.
Any perturbation to either the structure or function of an ecosystem.
Ectopic gene expression
Expression of a (trans)gene in a tissue where, or developmental stage when, such expression is not expected.
Introduction of DNA into a cell mediated by a brief pulse of electricity.
Embryonic stem (ES) cells
Cell lines derived from early embryos that have the potential to differentiate into all types of somatic cells as well as to form germ line cells, and hence whole animals, when injected into early embryos.
See Endogenous retrovirus.
Integrated retrovirus DNA (provirus) derived from infection of the germline of an ancestral animal. All animals are thought to carry numerous endogenous (but nonfunctional) retroviruses, some of which were inserted many millions of years ago.
Enucleated oocyte (cytoplast)
An egg cell from which the nucleus has been removed mechanically.
Viruses whose particles (virions) are surrounded by a lipid bilayer derived by budding from the cell membrane. Examples include retroviruses, herpesviruses, influenza viruses, and many more.
A common and usually benign herpesvirus that is the cause of infectious mononucleosis, but can cause life-threatening infection in immunosuppressed patients.
Refers to an individual or population that has returned to the wild after a history of domestication.
A type of relatively undifferentiated cell found in many parts of the body involved primarily in wound healing. Fibroblasts are relatively easy to grow in cell culture, and often are used for this purpose.
The ability to survive to reproductive age and produce viable offspring. Fitness also describes the frequency distribution of reproductive success for a population of sexually mature adults.
A state characterized by cells that have exited the cell cycle and entered into a resting phase.
A carbohydrate found as a modification to cell surface glycoprotein on all mammals (and many other organisms) except for old-world primates (including humans). The presence of naturally occurring antibodies to this modification in humans is a major (but not the only) cause of rejection of xenotransplanted organs.
The enzyme, lacking in old-world primates, responsible for adding galactose-1,3 galactose to proteins.
A species of retrovirus that includes PERV and MLV.
Refers to an organism whose genotype has been modified by application of biotechnology (e.g., gene transfer or chromosome set manipulation).
The proportional amount by which the average fitness of a population is depressed for genetic reasons below that of the genotype with maximum fitness.
The genetic identity of an individual. Genotype often is evident by outward characteristics.
Cells that contain inherited material that comes from the eggs and sperm, and that are passed on to offspring.
A substance or agent that, upon exposure, might result in a defined harm.
Helper, or packaging, cells
Cells engineered to express retrovirus packaging proteins to produce retroviruses capable of infecting cells when the packaging genes have been deleted from the retrovirus genome. Such cells are widely used for the production of retrovirus vectors. The retroviruses produced are incapable of making progeny that can infect cells.
In diploid organisms, one member of a pair of matching chromosomes.
Rearrangement of related DNA sequences on a different molecule by crossing over in a region of identical sequence.
Horizontal gene transfer
Transmission of DNA between species, involving close contact between the donor’s DNA and the recipient, uptake of DNA by the recipient, and stable incorporation of the DNA into the recipient’s genome.
IgE (immunoglobulin E)
A component of the human immune system implicated in the expression of allergies.
Regions of DNA that separate (or insulate) the expression of one region from that of the next.
The covalent joining of a piece of DNA (like a provirus) into genomic DNA.
Intracytoplasmic sperm injection (ICSI)
Fertilization by direct injection of sperm into the cytoplasm of an egg. ICSI can be used as a means of transfection.
Islets of Langerhans
The insulin-generating portion of the pancreas.
Replacement of a gene by a mutant version of the same gene using homologous recombination.
Inactivation of a gene by homologous recombination following transfection with a suitable DNA construct.
A method of transfection in which DNA is incorporated into lipid vesicles (liposomes), which then are fused to the membrane of the target cells.
Segments of DNA important for the correct and coordinated expression of large regions (such as those encoding hemoglobins).
Long terminal repeat (LTR)
A DNA sequence at the ends of the provirus (integrated DNA) of all retroviruses, derived during reverse transcription by duplication of sequences at the ends of the genome RNA. It contains most of the control elements necessary for expression of the provirus.
A transposon originally isolated from insects, but related elements have been found in many animals, including humans.
The introduction of DNA into the nucleus of an oocyte, embryo, or other cell by injection through a very fine needle.
The transfer of genes from one place to another (in the same or a different cell or organism) mediated by a retrovirus or transposable element.
Murine leukemia virus (MLV)
A retrovirus originally isolated from mice and widely used as the basis for retrovirus vectors.
A bacterial gene encoding resistance to several common antibiotics (kanamycin, neomycin, G418) widely used as a selectable marker in eukaryotic cells.
An organism’s place and function in the environment, defined by its utilization of resources.
Restoration of the correct embryonic pattern of gene expression in a nucleus derived from a somatic cell and introduced into an oocyte.
Nuclear transfer (NT)
The generation of a new animal nearly identical to another one by injection of the nucleus from a cell of the donor animal into an enucleated oocyte of the recipient.
The visible and/or measurable characteristics of an organism (i.e., how it appears outwardly) as opposed to its genotype, or genetic characteristics.
A circular DNA molecule capable of replication in bacteria. Plasmids are the usual means of propagation of DNA for transfection or other purposes.
A phenomenon whereby a particular gene affects multiple traits.
Large, positively-charged molecules often used to mediate transfection by reducing charge repulsion between DNA and the cell membrane.
Refers to a trait or phenotype whose expression is the result of the interaction of numerous genes.
Porcine endogenous virus (PERV)
Endogenous retrovirus of pigs closely related to MLV. Some PERVs can infect human cells.
Prion-related protein (PrP)
A normal protein, expressed in the nervous system of animals, whose structure when altered (by interaction with altered copies of itself) is the cause of scrapie in sheep, BSE in cattle, and Creutzfeldt-Jakob disease in humans.
Promoter and enhancer insertion
Activation of expression of a gene by integration of a nearby provirus, bringing expression of the gene under the control of regulatory elements in the LTR of the provirus.
A regulatory element that specifies the start site of transcription.
The use of a fine needle to inject DNA into the nucleus of an unfertilized egg.
The integrated DNA form of a retrovirus.
Refers to a genotype with a new combination of variable types, in contrast to parental type.
Recombinant DNA techniques
Procedures used to join together DNA segments in a cell-free system (an environment outside a cell or organism). Under appropriate conditions, a recombinant DNA molecule can enter a cell and replicate there, either autonomously or after it has become integrated into a cellular chromosome.
An enveloped virus that replicates by reverse transcription of its RNA genome into DNA, followed by integration of the DNA into the cell genome to form a provirus. Expression of the provirus (as though it were a cellular gene) leads to the production of progeny virus particles.
Vector constructs in which the internal genes of a retrovirus are replaced by the gene of interest, flanked by the viral LTRs and packaging signals. After transfection of helper cells, the vector is packaged into virus particles. Infection of target cells with these particles leads to integration of the gene into cellular DNA as part of a provirus.
The process of copying RNA into DNA, carried out by retroviral reverse transcriptase.
The likelihood of a defined hazard being realized, which is the product of two probabilities: the probability of exposure, P(E), and the probability of the hazard resulting given that exposure has occurred, P(H/E) (i.e., R = P(E) x P(H/E)).
A disease, originally of sheep, but transmissible to other animals, characterized by neurological degeneration due to accumulation of a structural variant of PrP.
The type of selection in which there is competition among males for mates and characteristics enhancing the reproductive success of the carrier are perpetuated irrespective of their survival value.
A gene, usually encoding resistance to an antibiotic, added to a vector construct to allow easy selection of cells that contain the construct from the large majority of cells that do not.
Animal cells that have nearly reached the limit of lifespan (usually around 50 doublings) in cell culture and are beginning to show signs of impending death.
Shutdown of transcription of a gene, usually by methylation of C residues.
A transposon related to mariner, originally isolated from fish.
The process through which a juvenile salmon becomes physiologically ready to enter salt water within its migratory life history.
Cells of body tissues other than the germline.
Introduction of DNA into an oocyte by first mixing it with sperm, which then is used for fertilization.
A brand of transgenic maize approved for animal feed only, but which also has been found in the human food supply.
DNA encoded on a plasmid of Agrobacterium that integrates into the genome of a plant cell after being introduced into the cell by fusion.
The enzyme, absent from most somatic cells but present in germline cells, that restores telomeres to their normal length.
The simple repeated sequences at the ends of chromosomes that protect them from loss of coding sequence during replication. In the absence of telomerase, telomeres become progressively shorter with each cell division, and this shortening is the major cause of senescence of cells in culture.
Alteration of the genome of a cell by direct introduction of DNA, a small portion of which becomes covalently associated with the host cell DNA.
A gene construct introduced into an organism by human intervention.
The enzyme responsible for moving a transposon from one place to another.
A DNA element capable of moving (transposing) from one location in a genome to another in the same cell through the action of transposase.
A gene that drives a population to extinction during the process of spread as a result of destructive, self-reinforcing cycles of natural selection.
A type of DNA, such as a plasmid or phage that is self-replicating and that can be used to transfer DNA segments among host cells. Also, an insect or other organism that provides a means of dispersal for a disease or parasite.
Inheritance of a gene from parent to offspring.
Virus in blood.
The extracellular form of a virus (i.e., a virus particle).
Transplantation of cells, tissues, or organs from one species to another.
Transmission of an infectious agent from an animal reservoir to humans.
A fertilized oocyte.