deoxyribonucleic acid(dee-OK-see-RY-boh-noo-KLEE-ik A-sid) The molecules inside cells that carry genetic information and pass it from one generation to the next.
Deoxyribonucleic Acid (DNA)(DNA)a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses.
deoxythymidineStrictly correct but rarely used synonym for thymidine.
derepressionThe process of "turning on" the expression of a gene or set of genes whose expression has been repressed (turned off), usually by the displacement of a…
DerivativeDerivatives are financial products, such as futures contracts, options, and mortgage-backed securities.
DesiccantAny compound used to remove moisture or water.
detergentSubstance which lowers the surface tension of a solution, improving its cleaning properties.
determinate growthGrowth determined and limited in time, with a bud or flower terminating the growth of the main axis. Once established, it is usually irreversible.
determinationProcess by which undifferentiated cells in an embryo become committed to develop into specific cell types, such as neurons, fibroblasts or muscle cells.
determinedDescribing embryonic tissue at a stage when it can develop only as a certain kind of tissue.
developmentThe sum total of events that contribute to the progressive elaboration of an organism. The two major aspects of development are growth and differentiation.
deviation1. An alteration from the typical form, function or behaviour. Mutation or stress are the common reasons behind deviation. 2.
dextrinAn intermediate polysaccharide compound resulting from the hydrolysis of starch to maltose by amylase enzymes.
dGTPAbbreviation for deoxyguanosine 5'-triphosphate. dGTP is required for DNA synthesis since it is a direct precursor molecule. See: guanosine, guanylic acid.
di-deoxynucleotide(Abbreviations: ddNTP,didN). A synthetic deoxynucleotide that lacks a 3'-hydroxyl group, and is thus unable to form the 3'?
DiabetesAny of several diseases in which the kidneys make a large amount of urine. Diabetes usually refers to diabetes mellitus in which there is also a high…
diabetes mellitus(dye-a-BEE-teez MEL-ih-tus) A group of disorders in which there is a defect in the transfer of glucose (sugar) from the bloodstream into cells, leading to…
diakinesisA stage of meiosis at the end of prophase I, in which the contraction of the chromosomes is almost at a maximum, pairing configurations are well defined…
dialysis(dye-AL-ih-sis) The process of filtering the blood when the kidneys are not able to cleanse it.
diazotrophAn organism that can fix atmospheric nitrogen.
dichogamyThe condition in which the male and the female reproductive organs of a flower (or certain hermaphroditic animals) mature at different times, thereby…
dicotyledon(Abbreviation: dicot). A plant with two cotyledons . One of the two major classes of flowering plants (along with the monocotyledons ).
Dideoxynucleotide (didN)A deoxynucleotide that lacks a 3' hydroxyl group, and is thus unable to form a 3'-5' phosphodiester bond necessary for chain elongation.
differential centrifugationA method for separating sub-cellular particles according to their sedimentation coefficients, which are roughly proportional to their size.
differential displayA method to identify mRNAs which are present at different levels in different tissues, or in response to specific treatments.
differentially permeableReferring to a membrane, through which different substances diffuse at different rates.
DifferentiationIn cancer, refers to how mature (developed) the cancer cells are in a tumor. Differentiated tumor cells resemble normal cells and tend to grow and spread…
diffusionThe spontaneous movement of molecules from a region of higher concentration to a region of lower concentration.
digestTo cut DNA molecules with one or more restriction endonucleases.
dihaploidAn individual which arises from a doubled haploid.
dihybridAn individual that is heterozygous for two pairs of alleles; the progeny of a cross between homozygous parents differing at two loci.
dimer1. A molecule formed by the covalent combination of two monomers, generally accompanied by elimination of water. 2.
dimethyl sulphoxide(Abbreviation: DMSO). A highly hygroscopic liquid and powerful solvent with little odour, colour or toxicity when pure.
dimorphismThe existence of two distinctly different types of individuals within a species. An obvious example is sexual dimorphism in mammals.
diplonemaStage in prophase I of meiosis following the pachytene stage, but preceding diakinesis, in which one pair of sister chromatids begin to separate from the…
direct embryogenesisThe formation in culture, on the surface of zygotic or somatic embryos or on explant tissues (leaf section, root tip, etc.
direct organogenesisFormation of organs directly on the surface of cultured intact explants . The process does not involve callus formation. Opposite: indirect organogenesis.
direct repeatTwo or more stretches of DNA within a single molecule which have the same nucleotide sequence in the same orientation.
directed amplification of minisatellite DNA(Abbreviation: DAMD). A polymerase chain reaction technique used for obtaining molecular markers in the region of minisatellites .
Directed differentiationManipulating stem cell culture conditions to induce differentiation into a particular cell type.
Directed evolutionA laboratory process used on isolated molecules or microbes to cause mutations and identify subsequent adaptations to novel environments.
Directed mutagenesisThe generation of changes in the nucleotide sequence of a cloned gene by one of several procedures.
Directed sequencingSuccessively sequencing DNA from adjacent stretches of chromosome.
Directional cloningDNA insert and vector molecules are digested with two different restriction enzymes to create noncomplementary sticky ends at either end of each…
disaccharideA dimer consisting of two covalently linked monosaccharides.
disarmThe deletion from a plasmid or virus of genes that are pathogenic.
discontinuous variationVariation where individuals can be classified as belonging to one of a set of discrete, non-overlapping classes.
discordantMembers of a pair showing different, rather than similar, characteristics.
disease resistanceThe genetically determined ability to prevent the reproduction of a pathogen, thereby remaining healthy.
Disease-associated genesAlleles carrying particular DNA sequences associated with the presence of disease.
disease-freeA plant or animal certified through specific tests as being free of specified pathogens .
disease-indexingDisease-indexed organisms have been assayed for the presence of known diseases according to standard testing procedures.
disinfectionAttempted elimination by chemical means of internal micro-organisms (particularly pathogens) from a culture or sample; rarely attained. See: sterilize (1).
disinfestationThe elimination or inhibition of the activity of surface-adhering micro-organisms and removal of insects.
disjunctionSeparation of homologous chromosomes during anaphase I of meiosis, or of sister chromatids during anaphase of mitosis and anaphase II of meiosis.
disomyThe presence of a pair of a specific homologous chromosomes. This is the norm for diploids.
dispenseThe transfer of a measured volume of a solution.
disrupter geneUsed to enforce the sterility of seed saved from a genetically engineered crop. See: genetic use restriction technology.
dissecting microscopeA microscope with a magnifying power of about 50x, used as an aid in the manipulation of small objects, e.g. excision of embryos from young zygotes.
dissectionSeparation of a tissue by cutting into components, for analysis or observation.
distillationThe process of heating a mixture to separate the more volatile from the less volatile parts, and then condensing fractions of the resulting vapour so as…
disulphide bridgeA chemical bond between pairs of sulphur atoms that stabilizes the three-dimensional structure of proteins, and hence the protein 's normal function.
ditypeIn fungi, a tetrad that contains two kinds of meiotic products (spores), e.g. 2AB and 2ab.
dizygotic twinsTwo-egg twins, i.e. a pair of individuals that shared the same uterus at the same time, but which arose from separate and independent fertilization of two…
DNAThe molecules inside cells that carry genetic information and pass it from one generation to the next. Also called deoxyribonucleic acid.
DNA (deoxyribonucleic acid)An organic acid and polymer composed of four nitrogenous bases--adenine, thymine, cytosine, and guanine linked via intervening units of phosphate and the…
DNA amplificationMany-fold multiplication of a particular DNA sequence either in vivo in a plasmid, phage or other vector; or in vitro using, most commonly, the polymerase…
DNA amplification fingerprinting(Abbreviation: DAF). A arbitrarily primed polymerase chain reaction technique for obtaining molecular markers using very short (5-8 bp) primers.
DNA bankA service that stores DNA extracted from blood samples or other human tissue.