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.