Base analogues - unnatural purine or pyrimidine bases that differ slightly in structure from the normal bases, but can be incorporated into nucleic acids. They are often mutagenic

Base collection - in PGR: Defined in the International Undertaking on Plant Genetic Resources (FAG, 1983) as a collection of seed stock or vegetative propagating material (ranging from tissue cultures to whole plants) held for long term security in order to preserve the genetic variation for scientific purposes and as a basis for plant. breeding as multiplication and evaluation. cf active collection

Base pair - the two strands that constitute DNA are held together by specific hydrogen bonding between purines and pyrimidines (A pairs with T; and G : pairs with C). The size of a : nucleic acid molecule is often described in terms of the. number of base pairs (symbolbp) or thousand base pairs (kilobase pairs; symbol: kb; a more convenient unit) it contains

Base substitution - replacement of one base by another in a DNA molecule

Basophil - a type of white blood cell (leucocyte), produced by stem cells in the red bone marrow

Batch culture - a suspension culture in which cells grow in a finite volume of liquid nutrient medium and follow a sigmoid pattern of growth. cf continuous culture; batch fermentation

Batch fermentation - a process in which cells or micro-organisms are grown for a limited time. At the beginning of the fermentation, an inoculum is introduced into fresh medium, with no addition or removal of medium for the duration of the process

Bench scale process - a small or laboratory scale process; commonly used in connection with fermentation

Biennial - in botany, a plant which completes its life cycle within two years and then dies. For most biennial plants, the two growing seasons have to be separated by a period of cold temperature sufficient to induce flowering and fruit formation

Bnary vector system - a two plasmid system in Agrobcterium tumefaciens for transferring into plant cells a segment of T DNA that carries cloned genes. One plasmid contains the virulence gene (responsible for transfer of the T DNA), and another plasmid contains the T DNA borders, the selectable marker and the DNA to be transferred

Binding - the ability of molecules to stick to each other because of the exact shape and chemical nature of parts of their surfaces. Many biological molecules bind extremely tightly and specifically to other molecules: enzymes to their substrates; antibodies to their antigens; DNA strands to their complementary strands; and so on. Binding can be characterised by a binding constant or association constant (Ka), or its inverse, the dissociation constant (Kd )

Binomial nomenclature - in biology, each species is generally identified by two terms the first is the genus to which it belongs, and the second is the specific epithet that distinguishes it from others in that genus (e.g., Quercus suber, cork oak). The genus name always has an initial capital; the specific epithet is never capitalized, even though it may be derived from a proper name (e.g., keranda nut, Elaeocarpus bancroftiz). Both terms in the binomial are italicized. Based on the system of classification developed by Carolus Linnaeus

Bio - a prefix derived from bios and used in scientific words to associate the concept of living organisms. Usually written with a hyphen before vowels, for emphasis or in neologisms; otherwise usually without a hyphen

Bio accumulation - in an organism, concentration of materials which are not components critical for that organisms survival. Usually it refers to the accumulation of metals or other compounds (e.g., DD1). Many organisms - plants, fungi, protists, bacteria, etc. accumulate metals when grown in a solution of them, either as part of their defence mechanism against. the poisonous effect of those compounds, or as a side-effect of the chemistry of their cell walls. Bio-accumulation is important as part of the microbial mining cycle (q.v.), removing toxic metals from wastewater, as a purification (bioremediation) process, etc

Bio assay - a procedure for the assessment of a substance by measuring its effect in living cells or on organisms. Animals have been used extensively in drug research in bio assays for the pharmacological activity of drugs. However, bio assays are now usually developed using bacteria or animal or plant cells, as these are usually much easier to handle than whole animals or plants, are cheaper to make and keep, and avoid the ethical problems associated with testing of animals. Sometimes used to detect minute amounts of substances that influence or are essential to growth

Bio augmentation - increasing the activity of bacteria that decompose pollutants; a technique used in bioremediation

Bio catalysis - use of enzymes to catalyse chemical reactions. See biotransformation

Bio control - the control of living organisms (especially pests) by biological means. Any process using deliberately introduced living organisms to restrain the growth and development of other, very often pathogenic, organisms, such as the use of spider mites to control cassava mealy bug, or the introduction of myxomatosis into Australia to control rabbits. The term also applies to use of disease-resistant crop cultivars. Biotechnology approaches biocontrol in various ways, such as using fungi, viruses or bacteria which are known to attack an insect or weed pest

Bio conversion - conversion of one chemical into another by living organism, as opposed to their conversion by enzymes (which is biotransformation) or by chemical processes. The usefulness of bioconversion is much the same as that of biotransformation in particular its extreme specificity and ability to work in moderate conditions. However, bioconversion has several other properties, including the possibility of having several chemical steps. A major commercial application is in the manufacture of steroids. The basic steroid molecule, often isolated from plants, is itself a very complicated molecule, and not one that is easy: to modify by normal chemical means to produce the very specific molecules need d for drug use. However, a particular type of bioconversion that. attacks only specific bits of the molecule can be used. Bioconversion is particularly useful for introducing chemical changes at specific points in large, complex molecules