Biotechnology Glossary

Biotechnology Glossary


A Adenine residue, in either DNA or RNA.



Ab See antibody.



abiotic stress The effect of non-living factors which can harm living organisms. These non-living factors include drought, extreme temperatures, pollutants, etc.



abscisic acid A plant growth regulator involved in abscission, dormancy, stomatal opening/closure, and inhibition of seed germination. It also affects the regulation of somatic cell embryogenesis in some plant species.



absciss; abscissa The horizontal axis of a graph. cf ordinate.



absorb (L. ab, away + sorbere, to suck in) To suck up, or to take in. In the cell, materials are taken in (absorbed) from a solution. cf adsorb.



absorption In general: the process of absorbing; taking up of water and nutrients by assimilation or imbibition. The taking up by capillary, osmotic, chemical or solvent action, such as the taking up of a gas by a solid or liquid, or taking up of a liquid by a solid. cf adsorption.



In biology: the movement of a fluid or a dissolved substance across a cell membrane.



In plants: water and mineral salts are absorbed from the soil by roots.



In animals: solubulized food material is absorbed into the circulatory system through cells lining the alimentary canal.



abzyme See catalytic antibody.



acaricide A pesticide used to kill or control mites or ticks.



accessory bud Lateral bud occurring at the base of a terminal bud or at the side of an axillary bud.



acclimatization The adaptation of a living organism (plant, animal or micro-organism) to a changed environment that subjects it to physiological stress. Acclimatization should not be confused with adaptation (q.v.). cf acquired.



acellular Describing tissues or organisms that are not made up of separate cells but often have more than one nucleus. cf syncytium.



acentric chromosome Chromosome fragment lacking a centromere.



acetyl co-enzyme A; acetyl CoA A compound formed in the mitochondria when an acetyl group (CH3CO-) - derived from breakdown of fats, proteins, or carbohydrates - combines with the thiol group (-SH) of co-enzyme A.



acquired Developed in response to the environment, not inherited, such as a character trait (acquired characteristic) resulting from environmental effect(s). cf acclimatization.



acridine dyes A class of positively charged polycyclic molecules that intercalate into DNA and induce frameshift mutations.



acrocentric A chromosome that has its centromere near the end.



acropetal 1. Developing or blooming in succession towards the apex, such as leaves or flowers developing acropetally.



2. Transport or movement of substances towards the apex, such as the movement of water through the plant.



The opposite tendency is termed basipetal.



acrosome An apical organelle in the head of a spermatozoon, q.v.



acrylamide gels See polyacrylamide gels.



actin One of the two contractile proteins in muscle (the other being myosin). Actin is also found in the microfilaments that form part of the cytoskeleton of all cells.



activated charcoal; activated carbon Charcoal which has been treated to remove hydrocarbons and to increase its adsorptive properties. It acts by condensing and holding a gas or solute onto its surface; thus inhibitory substances in nutrient medium may be adsorbed to charcoal included in the medium. Rooting factors such as phenolamines present as contaminants in charcoal may stimulate growth in vitro. Its addition to rooting medium may stimulate root initiation in some plant species. Activated charcoal may differ in origin and in composition. cf charcoal; phenolic oxidation.



active collection In PGR: Defined in the International Undertaking on Plant Genetic Resources (FAO, 1983) as a collection which complements a base collection (q.v.) and is a collection from which seed samples are drawn for distribution, exchange and other purposes such as multiplication and evaluation.



activator

1. A substance or physical agent that stimulates transcription of a specific gene or operon.



2. A compound that, by binding to an allosteric site on an enzyme, enables the active site of the enzyme to bind to the substrate. See gene expression.



active site

1. A site on the surface of a catalyst at which activity occurs.



2. The site on the surface of an enzyme molecule that binds the substrate molecule.



adaptation (L. ad, to + aptare, to fit) Adjustment of a population to changed environment over generations, associated (at least in part) with genetic changes resulting from selection imposed by the changed environment. Not acclimatization, q.v.



adaptation traits In AnGR: The complex of traits related to reproduction and survival of the individual in a particular production environment. Adaptation traits contribute to individual fitness; they are the traits subjected to selection during the evolution of animal genetic resources. By definition, these traits are also important to the ability of the animal genetic resource to be sustained in the production environment. (Based on FAO, 1999)



adaptive radiation The evolution of new forms, sub-species or species from one species of plant or animal in order to exploit new habitats or food sources. a.k.a. divergent evolution.



adaptor

1. A synthetic double-stranded oligonucleotide that has a blunt end, while the other end has a nucleotide extension that can base pair with a cohesive end created by cleavage of a DNA molecule with a specific type II restriction endonuclease. The blunt end of the adaptor can be ligated to the ends of a target DNA molecule and the construct can be cloned into a vector by using the cohesive ends of the adaptor.



2. A synthetic single-stranded oligonucleotide that, after self-hybridization, produces a molecule with cohesive ends and an internal restriction endonuclease site. When the adaptor is inserted into a cloning vector by means of the cohesive ends, the internal sequence provides a new restriction endonuclease site.



addendum (pl: addenda) In formulation of tissue culture media: an item or a constituent substance to be added.



additive allelic effects Effects of alleles at a locus, where the heterozygote is exactly intermediate between the two homozygotes.



additive gene effects Additive allelic effects summed across all the loci that contribute to genetic variation in a quantitative trait.



adenilate cyclase The enzyme that catalyses the formation of cyclic AMP.



adenine (C5H5N5; f.w. 135.14) (symbol: A) A white crystalline purine base. A constituent of DNA and RNA and nucleotides such as ADP and ATP. A B-group vitamin (B4) generally available as C5H5N5.3H2O, m.w. 189.13. It is added to some tissue culture media, as adenine sulphate, to promote shoot formation and for its weak cytokinin effect. It is present in plant tissues combined with aminoamide, phosphoric acids and D-ribose.



adenosine disphosphate (ADP) See ATP.



adenosine monophosphate (AMP) See ATP.



adenosine triphospate (ATP) See ATP.



adenovirus A group of DNA viruses which cause diseases in animals. In man, they produce acute respiratory tract infections with symptoms resembling common cold. They are used in gene cloning, as vectors for expressing large amounts of recombinant proteins in animal cells. They are also used to make live-virus vaccines against more dangerous pathogens. See viral vaccines.



ADEPT (antibody-directed enzyme pro-drug therapy) A way to target a drug to a specific tissue. The drug is administered as an inactive pro-drug, and then converted into an active drug by an enzyme administered with a second injection. The enzyme is coupled to an antibody that concentrates it in the target tissue. When the enzyme arrives at the target tissue, the pro-drug is activated to form the active drug, while elsewhere it remains inactive. See drug delivery; targeted drug delivery.



adhesion (L. adhaerere, to stick to) The attraction of dissimilar molecules for each other. A sticking together of unlike substances, such as soil and water.



A-DNA A right-handed DNA double helix that has 11 base pairs per turn. DNA exists in this form when partially dehydrated.



ADP (adenosine diphosphate) See ATP.