hormone(HOR-mone) One of many chemicals made by glands in the body. Hormones circulate in the bloodstream and control the actions of certain cells or organs.
hostIn a network, the central computer which controls the remote computers and holds the central databases.
host-specific toxinA metabolite, produced by a pathogen, and which is responsible for the adverse effects of the pathogen.
HSPOne of a group of proteins that help protect cells from stresses such as heat, cold, and low amounts of oxygen or glucose (sugar).
human artificial chromosome(Abbreviation: HAC). Analogous to yeast artificial chromosome, a construct comprising a human centromere and telomeres, which would allow for the cloning…
Human growth hormone (HGH, somatotrophin)A protein produced in the pituitary gland that stimulates the liver to produce somatomedins, which stimulate growth of bone and muscle.
hybrid dysgenesisInfertility and an increased incidence of chromosome mutations thought to be caused by the activation of transposons.
hybrid released translationA method used to identify the gene product of a cloned gene. The cloned DNA is immobilized and hybridized with a mixed mRNA sample, so that only mRNA…
hybrid seed1. Seed produced by crossing genetically dissimilar parents. 2. In plant breeding, used colloquially for seed produced by specific crosses of selected…
hybrid selectionThe process of choosing individuals possessing desired characteristics from among a hybrid population.
hybrid vigourThe extent to which a hybrid individual outperforms both its parents with respect to one or many traits.
HybridizationThe hydrogen bonding of complementary DNA and/or RNA sequences to form a duplex molecule. (See Northern hybridization, Southern hybridization.)
HybridomaA hybrid cell, composed of a B Iymphocyte fused to a tumor cell, which grows indefinitely in tissue culture and is selected for the secretion of a…
Hydrogen bondA relatively weak bond formed between a hydrogen atom (which is covalently bound to a nitrogen or oxygen atom) and a nitrogen or oxygen with an unshared…
hydrogen-uptake positive(Abbreviation: Hup+). A term describing a micro-organism that is capable of assimilating (or taking up) hydrogen gas.
HydrolysisA chemical reaction that uses water to break down a compound.
hydrophobic interactionAn interaction between a hydrophobic ('water-hating') part of a molecule and an aqueous environment.
hydroponicsThe growing of plants without soil. Plants are fed with an aerated solution of nutrients, and the roots are either supported within an inert matrix, or…
hygromycinAn antibiotic used as selective agent in bacterial and transgenic plant cell cultures.
hyperploidThe situation in which a particular chromosome or chromosome segment is present in more than the normal number. Opposite: hypoploid.
hypersensitive response1. A specific reaction of a plant to attack by a pathogen. The plant cells surrounding the point of infection rapidly die and dry out, so that pathogen…
hypersensitive siteRegions in the DNA that are highly susceptible to digestion with restriction endonucleases.
hypertonicA solution with an osmotic potential greater than that of living cells. Treatment with such solutions leads to the plasmolysis of cells.
hypervariable regionThe parts of both the heavy and light chains of an antibody molecule that enable it to bind to a specific site on an antigen.
hypervariable segmentA region of a protein that varies considerably between strains or individuals.
hypocotylThe portion of an embryo or seedling below the cotyledons . A transitional area between stem and root.
hypomorphA mutation that reduces, but does not completely abolish gene expression.
hypoplasticDefective and reduced growth or development (e.g. dwarfing and stunting in plants) resulting from an abnormal condition, for example disease or…
hypoploidThe situation in which a particular chromosome or chromosome segment is present in less than the normal number. Opposite: hyperploid.
hypothalamic peptidesPeptides generated in the vertebrate forebrain and concerned with regulating the body's physiological state.
hypotonicOsmotic potential less than that of living cells. Cells placed in a hypotonic solution will absorb water and display swelling and turgidity.
I/E regionAbbreviation for integration-excision region.
idiotypeAn identifying property or characteristic of an item or system. 1.A plant form expected on physiological grounds to represent an optimal type for the…
IGSAbbreviation for 1. internal guide sequence. 2. intergenic spacer.
imaginal discA mass of cells in the larvae of Drosophila melanogaster and other holometabolous insects that gives rise to particular adult organs, such as antennae…
imbibition1. The absorption of liquids or vapours into the ultramicroscopic spaces or pores found in materials. 2.
immobilized cellsCells entrapped in matrices such as alginate, polyacrylamide and agarose, for use in membrane and filter bioreactors.
immortalizationThe genetic transformation of a cell type into which can proliferate indefinitely.
Immortalizing oncogeneA gene that upon transfection enables a primary cell to grow indefinitely in culture. (See Oncogene.)
immune response(ih-MYOON reh-SPONTS) The activity of the immune system against foreign substances (antigens).
Immunity(ih-MYOO-nih-tee) The condition of being protected against an infectious disease.
immunizationA technique used to cause an immune response that results in resistance to a specific disease, especially an infectious disease.
immunoaffinity chromatographyA purification technique in which an antibody is bound to a matrix and is used to isolate a protein from a complex mixture. See: affinity chromatography.
immunoassayA test that uses the binding of antibodies to antigens to identify and measure certain substances. Immunoassays may be used to diagnose disease.
immunoglobulin(IH-myoo-noh-GLOB-yoo-lin) A type of protein that acts as an antibody.
immunoprophylaxisThe process of active or passive immunization. Active immunization with vaccines leads to long-term protection through mobilizing the organism's own…
immunosensorA biosensor having an antibody as the biological element.
immunosuppression(IH-myoo-noh-suh-PREH-shun) Suppression of the body's immune system and its ability to fight infections and other diseases.
immunosuppressorA substance, an agent or a condition that prevents or diminishes the immune response.
immunotherapy(IH-myoo-noh-THAYR-uh-pee) Treatment to boost or restore the ability of the immune system to fight cancer, infections, and other diseases.
immunotoxin(IH-myoo-noh-TOK-sin) An antibody linked to a toxic substance. Some immunotoxins can bind to cancer cells and kill them.
ImpellerAn agitator that is used for mixing the contents of a bioreactor.
in silicoIn a computer file. In the present context, the use of data bases of DNA and protein sequence to help answer biological questions.
In situ(in si'too) the natural or normal place; confined to the site of origin without invasion or spread to neighboring tissues.
in situ colonyhybridization A procedure for screening bacterial colonies or plaques growing on plates or membranes for the presence of specific DNA sequences by the…
in situ hybridizationThe visualization of in vivo location of macromolecules (particularly polynucleotides and polypeptides) by the histological staining of tissue sections or…
In vitro(in VEE-troh) In the laboratory (outside the body). The opposite of in vivo (in the body).
in vitro embryo production(Abbreviation: IVEP). The combination of ovum pickup, in vitro maturation of ova, and in vitro fertilization.
In vitro fertilization(in VEE-troh FER-tih-lih-ZAY-shun) A procedure in which eggs are removed from a woman's ovary and combined with sperm outside the body to form embryos.
in vitro maturation(Abbreviation: IVM). Culture of immature ova in the laboratory, usually until they are ready for in vitro fertilization.
in vitro transcriptionThe cell-free synthesis from DNA of RNA in the test tube. Synonym: cell-free transcription.
in vitro translationThe synthesis of proteins from isolated mRNA molecules in the test-tube. Synonym: cell-free translation.
In vivoIn the body. The opposite of in vitro (outside the body or in the laboratory).
in vivo gene therapyThe delivery of a gene or genes to a tissue or organ of a complete living individual to alleviate a genetic disorder.
in-situ conservationThe conservation of ecosystems and natural habitats and the maintenance and recovery of viable populations of species in their natural surroundings and…
inactivated agentA virus, bacterium or other organism that has been treated to prevent it from causing a disease. See: attenuated vaccine.
inbred lineThe product of inbreeding, i.e. the intercrossing of individuals that have ancestors in common.
inbreedingMatings between individuals that have one or more ancestors in common, the extreme condition being self-fertilization, which occurs naturally in many…
inbreeding depressionThe reduction in vigour over generations of inbreeding. This affects species which are normally outbreeding and highly heterozygous. See: hybrid vigour.
inclusion bodyA protein that is overproduced in a recombinant bacterium and forms a crystalline structure inside the bacterial cell.
incompatibility1. Genetically or physiologically determined prevention of intermating. 2. A physiological interaction resulting in graft rejection or failure. 3.
incompatibility groupPlasmids must belong to different incompatibility groups to co-exist within the same cell.
Incomplete dominanceA condition where a heterozygous offspring has a phenotype that is distinctly different from, and intermediate to, the parental phenotypes.
incomplete penetranceWhere the phenotype does not allow perfect prediction of the genotype as a result of interference in gene expression by the environment.
incubation1. The hatching of eggs by means of heat, either natural or artificial. 2. Period between infection and appearance of symptoms induced by a pathogen. 3.
incubatorAn apparatus in which environmental conditions (light, photoperiod, temperature, humidity, etc.
indehiscentDescribing a fruit or fruiting body that does not open to release its seeds or spores when ripe.
Independent assortmentThe random distribution during meiosis of alleles (at different genes) to the gametes that is the case when the genes in question are located on different…
indeterminate growthThe condition in which the terminal bud persists and produces successive lateral branches over an indefinite period. Opposite: determinate growth.