ascites(uh-SY-teez) Abnormal buildup of fluid in the abdomen that may cause swelling. In late-stage cancer, tumor cells may be found in the fluid in the abdomen.
ascosporeOne of the spores contained in the ascus of certain fungi.
ascus(pl.: asci) Reproductive sac in the sexual stage of a type of fungi (Ascomycetes) in which ascospores are produced.
asepticSterile, free of contaminating organisms (bacteria, fungi, algae but not generally including viruses, and particularly not internal symbionts ).
asexualReproduction not involving meiosis or the union of gametes.
asymmetric hybridA hybrid formed, usually via protoplast fusion, between two donors, where the chromosome complement of one of the donors is incomplete.
asynapsisThe failure or partial failure in the pairing of homologous chromosomes during the first meiotic prophase.
ATPA substance present in all living cells that provides energy for many metabolic processes and is involved in making RNA.
ATP-aseAn enzyme that brings about the hydrolysis of adenosine triphosphate, by the cleavage of either one phosphate groups with the formation of ADP and…
attenuated vaccineA virulent organism that has been modified to produce a less virulent form, but nevertheless retains the ability to elicit antibodies against the virulent…
AttenuationA mechanism for controlling gene expression in prokaryotes that involves premature termination of transcription.
attenuatorA nucleotide sequence in the 5' region of a prokaryotic gene (or in its RNA ) that causes premature termination of transcription, possibly by forming a…
aureofacinAn antifungal antibiotic produced by a strain of Streptomyces aureofaciens. A possible candidate for the transgenic control of plant fungal disease.
authentic proteinA recombinant protein that has all the properties - including any post-translational modifications - of its naturally occurring counterpart.
auto-immune diseaseDisorder in which the immune systems of affected individuals produce antibodies against molecules that are normally produced by those individuals (called…
auto-immunityA disorder in the body's defence mechanism in which an immune response is elicited against its own (self) tissues.
autocatalysisCatalysis in which one of the products of the reaction is a catalyst for the reaction.
autoclave(AW-toh-KLAYV) A device that uses steam under high pressure to sterilize medical and laboratory supplies and equipment.
autogenous controlThe action of a gene product to inhibit (negative autogenous control) or enhance (positive autogenous control) the expression of the gene that codes for…
autologous cellsCells taken from an individual, cultured (or stored), and, possibly, genetically manipulated before being transferred back into the original donor.
autolysisThe process of self destruction of a cell, cell organelle, or tissue, through the action of lysosomic enzymes.
autonomousA term applied to any biological unit that can function on its own, i.e. without the help of another unit, such as a transposable element that encodes an…
autopolyploidA polyploid whose constituent genomes are derived from the same or nearly the same progenitor.
autoradiographA technique for visualizing the presence, location and intensity of radioactivity in histological preparations, paper chromatograms or electrophoretic gel…
AutosomeA chromosome that is not involved in sex determination.
autotrophOrganism capable of self-nourishment utilizing carbon dioxide or carbonates as the sole source of carbon and obtaining energy from radiant energy or from…
auxinA group of plant growth regulators (natural or synthetic) which stimulate cell division, enlargement, apical dominance, root initiation, and flowering.
auxin-cytokinin ratioThe relative proportion of auxin to cytokinin present in plant tissue culture media.
auxotrophA mutant cell or micro-organism lacking one metabolic pathway present in the parental strain, and that consequently will not multiply on a minimal medium…
AvailabilityA reflection of the form and location of nutritional elements and their suitability for absorption.
avidinA glycoprotein present in egg white, which has a strong affinity to biotin. Can lead to biotin deficiency if given in large quantities.
avidityA measure of the binding strength of an antibody to its antigen.
avirulence gene(Abbreviation: avr gene). Many plants contain R genes, which confer simply-inherited resistance to a specific pathogen race.
axenic cultureFree of external contaminants and internal symbionts; generally not possible with surface sterilization alone, sometimes used incorrectly to indicate.
axillary budA bud found at the axil of a leaf. Synonym: lateral bud.
axillary bud proliferationPropagation of plant tissue in vitro to promote axillary growth, to generate large numbers of plantlets in culture.
B cellA white blood cell that comes from bone marrow. As part of the immune system, B cells make antibodies and help fight infections. Also called B lymphocyte.
B chromosomeA supernumerary chromosome present in some individuals (both plant and animal).
B lymphocyteA white blood cell that comes from bone marrow. As part of the immune system, B lymphocytes make antibodies and help fight infections. Also called B cell.
BABSAbbreviation for biosynthetic antibody binding sites.
BACAbbreviation for bacterial artificial chromosome.
Bacillus thuringiensis(Abbreviation: Bt). A bacterium that produces a toxin against certain insects, particularly Coloeoptera and Lepidoptera; a major means of insecticide for…
Bacillus thuringiensis (Bt)A bacterium that kills insects; a major component of the microbial pesticide industry.
back mutationA second mutation at the same site in a gene as the original mutation. The second mutation restores the wild-type protein sequence.
BackcrossCrossing an organism with one of its parent organisms.
bacterial artificial chromosomeA plasmid vector that can be used to clone large inserts of DNA (up to 500 kb). See: yeast artificial chromosome.
bacterial toxin(bak-TEER-ee-ul TOK-sin) A toxic substance, made by bacteria, that can be modified to kill specific tumor cells without harming normal cells.
BacteriocideA class of antibiotics that kills bacterial cells.
bacteriocinA protein produced by bacteria of one strain and active against those of a closely related strain.
Bacteriophage(Abbreviation: phage). A virus that infects bacteria. Altered forms are used as cloning vectors. See: lambda phage, M13.
baculovirusA class of insect virus used to make DNA cloning vectors for gene expression in eukaryotic cells.
baculovirus expression vector(Abbreviation: BEV). A method for the in vitro production of complex recombinant eukaryotic protein s.
balanced lethal systemA system for maintaining a recessive lethal allele at each of two loci on the same pair of chromosomes.
balanced polymorphismTwo or more phenotypes maintained in the same breeding population.
BankAmerica has a "dual banking system" which means that both states and the federal government issue bank charters for the need and convenience of their…
barnaseA bacterial ribonuclease, which, when transformed into plants and expressed in the anthers, generates a male sterile phenotype.
Barr bodyA condensed mass of chromatin found in the nuclei of female mammals. It is a late-replicating, inactive X-chromosome. See: dosage compensation, sex linkage
basal1. Located at the base of a plant or a plant organ. 2. A fundamental formulation of a tissue culture medium containing nutrients but no growth promoting…
baseOne of the components of nucleosides, nucleotides and nucleic acids . Four different bases are found in naturally occurring DNA - the purines A (adenine )…
base analogueA non-natural purine or pyrimidine base that differs slightly in structure from the normal bases, but can be incorporated into nucleic acids .
base paircombination of 2 nucleotides (A and T or G and C) held together by weak hydrogen bonds; the DNA double helix is formed when a base pair of nucleotides in…
Base pair (bp)A pair of complementary nitrogenous bases in a DNA molecule--adenine-thymine and guanine-cytosine. Also, the unit of measurement for DNA sequences.
base substitutionReplacement of one base by another in a DNA molecule. See: transition; transversion.
binary vector systemA two plasmid system in Agrobacterium tumefaciens designed to transfer T-DNA into plant cells, while avoiding the formation of crown gall tumours.
bindingThe ability of molecules to bind each other non-covalently because of the exact shape and chemical nature of parts of their surfaces.
bio-A prefix used in scientific words to associate the concept of "living organisms.
bio-accumulationA problem that can arise when a stable chemical such as a heavy metal or DDT is introduced into a natural environment.
bio-assay1. The assessment of a substance's activity on living cells or on organisms. Animals have been used extensively in drug research in bio-assays in the…
bio-augmentationIncreasing the activity of bacteria that decompose pollutants; a technique used in bioremediation.