Science and Development Network
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Definitions
Below is a directory of terms used in the field of genetically modified crops. Most of the terms have been reproduced from the University of California Biotech [UCB] or John Innes Centre [JIC].
A
Agrobacterium
A naturally occurring soil microorganism (bacterium) that produces crown gall disease in the wild; it does so by introducing part of its genetic material into the plant to direct it to make compounds it needs to live. A small piece of genetic material was isolated from this bacterium and is used to insert genes into plants in the process of genetic modification. [UCB]
Allergy
Adverse overreaction of the body's self-defence system, caused by the production of antibodies against specific substances. Asthma, hayfever and intolerance to milk or egg are familiar examples of allergies. [JIC]
Amino acids
Building blocks of proteins. About 20 different amino acids are commonly used by cells to make proteins. [JIC]
Antibiotic
Chemical substance produced by some bacteria and fungi, or produced synthetically, that inhibits the growth of, or kills, other microorganisms.
Antibiotic resistance
Resistance mechanisms to antibiotics exist that render cells 'immune' to the antibiotic; the genes for these characteristics are found in certain organisms. The genes are used in some genetic engineering experiments as tools to identify cells that have received new DNA. [UCB]
Antibodies
A class of proteins (known as immunoglobulins) formed in the body in response to the presence of antigens (foreign proteins and other compounds), which bind to the antigen and inactivate it. [JIC]
B
Bacillus thuringiensis (Bt)
A naturally occurring microorganism that produces a toxin that only kills organisms with alkaline stomachs, namely insect larvae. The toxin (in the form of a whole killed organism) has been used for biological control for decades. The genetic information that encodes the toxin has now been indentified and moved into plants to make them insect tolerant.
Bacterium
Simplest form of life that exists as a single cell without a nucleaus (distinct structure that contains the genetic information of the cell). Also known as a prokaryote. [UCB]
Bases
Building blocks of DNA made up of nitrogen and carbon atoms. There are two types of bases: purines (adenine and guanine, known as A and G) and pyrimidines (cytosine and thymine, known as C and T). The bases pair up in the DNA double helix, and the order of bases determines the genetic code. [JIC]
C
Chromosome
A thread-like structure, consisting mostly of DNA and supporting proteins, that contains the genetic information (in the form of genes) that instruct the cell on its function. Genes are arranged in a particular order on chromosomes. Chromosomes are found in the nucleus of the cell and organisms contain differing but characteristic numbers of chromosomes, which are arranged in pairs in 'higher' plants and animals.
Cloning
Means of isolating particular parts of the genome as small fragments of DNA, and making copies of and studying the sequence in another organism. Can also mean the process of producing, by non-sexual means, an identical copy of an organism. [UCB]
D
DNA
Deoxyribonucleic acid. The chemical building block of the genetic information in the cell from which genes are composed; it specifies the characteristics of most living organisms. DNA consists of a long molecule of repeating units (each unit containing deoxyribose (a sugar), a phosphoric acid and a base) joined together in a particular order. DNA is usually found as two complementary strands twisted into the shape of a double helix.
DNA code
The sequence (order) of DNA bases in a gene, which make up the instructions for a particular characteristic of the organism. [JIC]
G
Gene
The segment of DNA on a chromosome that contains the information necessary to make a protein. Genes are the unit by which biological traits are inherited. [JIC]
Gene flow
The incorporation of genes from one organism into the array of genes in another population of organisms. [UCB]
Gene mapping
Determination of the relative locations of genetic information (genes) on chromosomes. [UCB]
Gene modification
The manipulation of a living organism's genetic make-up by eliminating, modifying or adding copies of specific genes (often from other oganisms) through modern molecular biology techniques. Also called 'gene splicing', 'recombinant DNA (rDNA) technology' or 'genetic engineering'. [JIC]
Genetically modified organism (GMO)
Term used to refer to an organism modified by the methods of genetic modification. [UCB]
Genetics
Study of the pattern of inheritance of genetic information in organisms. [UCB]
Genome
Entire genetic material in an organism, comprising all chromosomes. [UCB]
Genomics
Molecular characterisation of all the genes and gene products of a species. [UCB]
H
Herbicide
Any chemical substance that is toxic to plants; usually used to kill specific unwanted plants, especially weeds. [JIC]
I
Insecticide
A chemical used to kill or control certain populations of insect pests. In agriculture, insecticides are used to control insect pests that feed on crops or carry plant disease. [JIC]
M
Marker
Identifiable physical location on a chromosome, the inheritance of which can be monitored. Antibiotic resistance marker genes (usually of bacterial origin) render cells "immune" to the antibiotic; these genes can be used as tools to identify plant cells that have received new DNA through genetic modification.
Mutant
Organism that differs from its parent because of a mutation in its genetic code. Also called a variant.
Mutation
Genetic change caused by natural phenomena or an agent that causes mutations (such as radiation). 'Stable' mutations in genes are passed on to an organism's offspring; 'unstable' mutations are not. [UCB]
N
Nucleotide
Strings of thousands of nucleotides form a DNA or RNA molecule. Nucleotides are composed of phosphate, sugar and one of four bases (adenine, guanine, cytosine, and uracil or thymine). Three bases form a codon, which specifies a particular amino acid; amino acids are strung together to form proteins. [UCB]
Nucleus
Central compartment in cells of 'higher' organisms (eukaryotes); it houses most of the heritable genetic information in the cell. [UCB]
P
Pathogen
Any organism capable of producing disease. [UCB]
Pesticide
A chemical substance (such as an insecticide or fungicide) that kills harmful organisms and is used to control pests, such as insects, weeds, or microorganisms. [JIC]
Plasmid
Independent, free-floating circular piece of DNA in a bacterium, capable of making copies of itself in a host cell. Plasmids can be used in genetic modification experiments to clone genes from other organisms and make large quantities of their DNA. [UCB]
Promoter
A control region of a gene that determines in which tissue, and at when, a gene product is produced. [UCB]
R
Ribonucleic acid (RNA)
Chemical chains made up of the sugar ribose attached to a phosphoric acid and a base. Different types of RNA exist in cells, some of which serve as the immediate code for proteins, others of which are involved in the physical process of protein synthesis. RNA can also serve instead of DNA as the only genetic information in certain viruses.
T
Tissue culture
Process of introducing living tissue into culture in the laboratory, where tissues or cells can be grown for extended periods of time. [UCB]
Transformation
Process of introducing into an organism new genetic information that can be stably maintained. [UCB]
Transgenic plant
Genetically modified plant, or offspring of genetically modified plants. The transgenic plant usually contains genetic material that has been rearranged, or a foreign gene (a transgene) from an unrelated organism such as a virus, animal or other plant. [JIC]
V
Vaccine
Use of a killed or debilitated organism, or a part of its contents, that is capable of inducing protection against the disease caused by that organism. Scientists are working to develop oral vaccines which can be produced in the edible plants of transgenic plants (e.g. fruits).
Value-added
Trait introduced into an organism or plant that gives that organism added value, such as the capability to produce a pharmaceutical substance. [UCB]
Virus
Small genetic element, composed of either DNA or RNA, that is protected by a protein coat. Viruses cannot make copies of themselves without invading another (host) cell, and using some of its cellular machinery. A virus is capable of existing either inside or outside a host cell. [UCB]
