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- F -

F factor  A bacterial episome that confers the ability to function as a genetic donor in conjugation; the fertility factor in bacteria.

F1  The first filial generation in a cross between any two parents; the first generation of descent from a given mating.

F2  The second filial generation, produced by crossing two members of the F1, or by self-pollinating the F1. The "grandchildren" of a given mating.

FACS  See fluorescence-activated cell sorting.

factorial mating  A mating scheme in which each male parent is mated with each female parent. Made possible in animals by means of in vitro embryo production (q.v.). Such a mating scheme substantially reduces the rate of inbreeding in a selection programme.

FAD (flavin adenine dinucleotide)  A co-enzyme important in various biochemical reactions. It comprises a phosphorylated vitamin B2 (riboflavin) molecule linked to the nucleotide adenine monophosphate (AMP). It functions as a hydrogen acceptor in dehydrogenation reactions, being reduced to FADH2. This in turn is oxidized to FAD by the electron transport chain, thereby generating ATP (two molecules of ATP per molecule of FADH2).

false fruit  See pseudocarp.

false-negative  A negative assay result that should have been positive.

false-positive  A positive assay result that should have been negative.

farm animal genetic resources (AnGR)  In AnGR: Those animal species that are used, or may be used, for the production of food and agriculture, and the populations within each of them. These populations within each species can be classified as wild and feral populations, landraces and primary populations, standardized breeds, selected lines, and any conserved genetic material. (Source: FAO, 1999)

farm animal genetic resources utilization  See utilization of farm animal genetic resources.

fascicle  See vascular bundle.

fed-batch fermentation  Culture of cells or micro-organisms where nutrients are added periodically to the bioreactor.

feedback inhibition  The process by which the accumulated end product of a biochemical pathway stops synthesis of that product. A late metabolite of a synthetic pathway regulates synthesis at an earlier step of the pathway. cf end-product inhibition.

fermentation  The anaerobic breakdown by micro-organisms of complex organic substances, especially carbohydrates like glucose. The process is energy-yielding. Fermentation is often misused to describe large-scale aerobic cell culture in specialized vessels (fermenters, bioreactors) for secondary product synthesis.

fermentation substrates  Materials used as food for growing micro-organism. The fermentation substrates and the trace materials needed, together with chemicals added to make the fermentation easier, form the culture medium.

fermenter  See bioreactor.

fertile  Of an organism: Capable of breeding and reproduction.

fertilization  (L. fertilis, capable of producing fruit)  The union of two gametes from opposite sexes to form a zygote; it involves the fusion of nuclei of gametes (karyogamy) and the fusion of cytoplasm (plasmogamy). Typically, each gamete contains a haploid set of chromosomes. Hence, after fusion of the nuclei, the resulting nucleus contains a diploid set of chromosomes.

    Several categories are distinguished:

    1. Self-fertilization (selfing) - fusion of male and female gametes from the same euploid organism.

    2. Cross-fertilization (crossing) - fusion of male and female gametes from different euploid individuals.

    3. Double fertilization - in angiosperms, the fusion of one male gamete with the ovum at about the same time as the second male gamete fuses with the female polar nuclei (or secondary nucleus) to form the endosperm.

fertilizer  Any substance that is added to soil in order to increase its productivity. Fertilizers can be of natural origin, such as composts, or they can be inorganic (artifical fertilizer) chemical, particularly nitrates and phosphates.

fetus  See foetus.

Feulgen's test  A histochemical test in which the distribution of DNA in the chromosomes of dividing cell nuclei can be observed. A tissue section is first treated with dilute hydrochloric acid to remove the purine bases of the DNA, thus exposing the aldehyde groups of the sugar deoxyribose. The section is then immersed in Schiff's reagent, which combines with the aldehyde groups to form a magenta-coloured compound.

F factor  A bacterial episome that confers the ability to function as a genetic donor in conjugation; the fertility factor in bacteria.

fibres  Elongated cells with tapering, pointed ends; the cells interlock to form a strong, rigid tissue; pits in the walls are usually very narrow and not very numerous.

fibril  Microscopic to sub-microscopic cellulose thread that is part of the cellulose matrix of plant cell walls.

fibrous root  Root system in which both primary and lateral roots have approximately equal diameters. Opposite is tap root.

field gene bank See gene bank (2).

filial generation. See F1; F2.

filter bioreactor; mesh bioreactor  Cells are grown on an open mesh of an inert material, which allows the culture medium to flow past it but retains the cells. This is similar in idea to membrane and hollow fibre reactors, but can be much easier to set up, being similar to conventional tower bioreactors, but with the meshwork replacing the central reactor space.

filter sterilization  Process of sterilizing a liquid by passage through a filter with pores so small that they prevent the passage of micro-organisms and microbial spores.

filtration  1. Separation of solids from liquids by using a porous material that only allows passage of the liquid or of solids of a smaller than the pore size of the filter. The material passing the filter forms the filtrate.

    2. Removal of cell aggregates to obtain a filtrate of single cells that can be utilized as plating inocula.

fission  (L. fissilis, easily split)  Asexual reproduction involving the division of a single-celled individual into two new single-celled individuals of equal size.

fitness  The number of offspring left by an individual, often compared with the average of the population or with some other standard, such as the number of offspring left by a particular genotype.

fixation  An event that occurs when all the alleles at a locus except one are eliminated from a population. The remaining allele, now occurring with a frequency of 100%, is said to have been fixed.

FLAG  See affinity tag.

flagellum (pl: flagella; adj: flagellate)  A whiplike organelle of locomotion in certain cells; locomotor structures in flagellate protozoa.

flaming  A technique for sterilizing instruments. The instrument is dipped in alcohol (usually 95% (v/v) ethanol) and then the alcohol on the instrument is ignited, thus heat-sterilizing the tool surface.

flanking region  The DNA sequences extending either side of a specific sequence.

floccule  Micro-organism aggregate or colloidal particle floating in or on a liquid. Contaminated liquid media are usually cloudy, illustrating this flocculation phenomenon.

flocculant  Agent that causes small particles to aggregate (flocculate).

fluorescence in situ hybridization (FISH)  Hybridization of cloned DNA to intact chromosomes, where the cloned DNA has been labelled with a fluorescent dye. This is the major method of physical mapping of cloned DNA fragments on chromosomes.

fluorescence-activated cell sorting (FACS)  The use of laser beams to detect differences in fluorescence between different types of cells in a mixture, and the subsequent deflection of cells into separate bins corresponding to each type of cell in the mixture. One of the popular uses of this technology is in sperm sexing (q.v.).

fluorescent probe  Probe whose response is based on the fluorescence intensity of individual cells or cell components.

flow cytometry  A technique used to sort cells or other biological materials by means of flow through apertures of defined size or by laser sorting.

flower  The structure in angiosperms (flowering plants) that bears the organs for sexual reproduction.

flush end  See blunt end.

flush-end cut  See blunt-end cut.

foetus  Pre-natal stage of a viviparous animal, between the embryonic stage and parturition.

food processing enzyme  Enzyme used to control food texture, flavour, appearance and, to a certain extent, nutritional value. Amylases break down complex polysaccharides to simplex sugars; proteases tenderize meat proteins. Biotechnology can assist the development of new food enzymes by finding or engineering enzymes which fit better with the other processes which the food must undergo, like cooking or canning.

fog  Fine particles of liquid suspended in the air, such as of water in a fog chamber used for acclimatizing recent ex vitro transplants. cf mist propagation.

fold-back  The structure formed when a double-stranded DNA molecule containing an inverted repeat sequence is denatured and then allowed to re-anneal at low DNA concentrations. The repeated sequence permits the formation of a double-stranded region within each of the separated strands of the original molecule.

folded genome  The condensed intracellular state of the DNA in the nucleoid of a bacterium. The DNA is segregated into domains, and each domain is independently negatively supercoiled.

follicle  Any enclosing cluster of cells that protects and nourishes a cell or structure within. Thus a follicle in the ovary contains a developing egg cell, while a hair follicle envelops the root of hair.

follicle stimulating hormone (FSH)  A hormone, secreted by the anterior pituitary gland in mammals, that stimulates, in female mammals, ripening of specialized structures in the ovary (Graafian follicles) that produce ova and, in males, the formation of sperm in the testis. It is a major constituent of fertility drugs.

foot-candle  An obsolete photometric measure of light intensity. Now superseded by the lux (symbol: lx) (1 fc 10.7 lx). See lux; photon.

forced cloning  The insertion of foreign DNA into a cloning vector in a predetermined orientation.

foreign DNA  A DNA molecule that is incorporated into either a cloning vector or a chromosomal site. See exogenous DNA.

fortify  To add strengthening components or beneficial ingredients to a nutrient medium.

formulation  1. For traditional therapeutic agents, this refers to the method by which a therapeutic agent is delivered to its site of action.

    2. For tissue culture, see medium; medium formulation.

fouling  The coating or plugging (by materials or micro-organisms) of equipment, thus preventing it from functioning properly.

founder animal  In transgenesis research, an organism that carries a transgene in its germ line and can be used in matings to establish a pure-breeding transgenic line, or one that acts as a breeding stock for transgenic animals.

founder principle  The possibility that a new, small, isolated population may be genetically different from the "parent" population, because the founding individuals (being a small, random sample from the large, "parent" population) could be quite different from typical members of the "parent" population.

four-base cutter; four-base-pair-cutter; four-cutter  A type II restriction endonuclease that binds (and subsequently cleaves) DNA at sites that contain a sequence of four nucleotide pairs that is uniquely recognised by that enzyme. Because any sequence of four bases occurs more frequently by chance than any sequence of six bases, four-base cutters cleave more frequently than do six-base cutters. Thus, four-base cutters create smaller fragments than six-base cutters.

fractionation  Separation.

fragment  See restriction fragment.

frameshift mutation  A mutation that changes the reading frame of an mRNA, either by inserting or deleting nucleotides.

free-living conditions  Natural or greenhouse conditions where the plantlets are transferred from in vitro conditions to soil mixtures. In such instances, plantlets must manufacture their own food supply for survival. See acclimatization; hardening off.

free water  Water released by a cell when freezing occurs in intercellular spaces. cf bound water.

freeze-drying  The process of drying a tissue or an organ in a frozen state under vacuum. Tissues are freeze-dried to measure their dry weight or to preserve them for future analysis. Freeze-drying is the standard way of preserving micro-organisms for long periods of time. cf lyophilization.

freeze preservation  See cryobiological preservation.

frequency distribution  A graph showing either the relative or absolute incidence of classes in a population. The classes may be defined by either a discrete or a continuous variable; in the latter case, each class represents a different interval on the scale of measurement.

fresh weight  The weight, including the water content, of a plant or plant part at the time of harvest. cf wet weight.

friable  A term commonly used to describe a crumbling or fragmenting callus. A friable callus is easily dissected and readily dispersed into single cells or clumps of cells in solution.

FSH  See follicle stimulating hormone.

functional gene cloning  See candidate gene strategy.

fungicide  An agent, such as a chemical, that kills fungi.

furfural; furfuraldehyde  Used industrially as a solvent and as a raw material for synthetic resin.

fusion biopharmaceuticals  Biopharmaceutical proteins formed as a result of fusion proteins. Their advantages are:

    - synergistic activities in one molecule; thus when the molecule binds to a cell, it does two things at once;

    - the adverse effect or poor stability of one molecule may be offset by the properties of the other; and

    - one molecule acts as a targeting mechanism to bring the other to the site where it is meant to act.

      See fusion protein: immunotoxin.

fusion gene  A hybrid gene created by joining portions of two different genes (to produce a new protein) or by joining a gene to a different promoter (to alter or regulate gene transcription).

fusion protein  A polypeptide made from a recombinant gene that contains portions of two or more different genes. The different genes are joined so that their coding sequences are in the same reading frame: the genetic apparatus reads the gene fusion as a single gene, and so produces a fusion protein. Also known as hybrid protein or chimeric protein. These proteins are used:

      - to add an affinity tag to a protein;

      - to produce a peptide as part of a larger protein, which is then cut up after it has been made by cloning;

      - to produce a protein with the combined characteristics of two natural proteins; or

      - to produce a protein where two different activities are physically linked.

      See affinity tag; fusion biopharmaceutical.

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