DNA polymorphismOne of two or more alternate forms (alleles) of a chromosomal locus that differ in nucleotide sequence or have variable numbers of repeated nucleotide…
DNA primaseAn enzyme that catalyses the synthesis of the short strands of RNA that initiate the synthesis of DNA strands.
DNA repairA variety of mechanisms that repair errors (e.g. the incorporation of a non-complementary nucleotide) that occur naturally during DNA replication.
DNA repair genesGenes encoding proteins that correct errors in DNA sequencing.
DNA replication(⦠reh-plih-KAY-shun) The process by which a copy of the DNA in a cell is made before the cell divides.
DNA sequenceThe relative order of base pairs, whether in a DNA fragment, gene, chromosome, or an entire genome. See also: base sequence analysis
DNA sequencingProcedures for determining the nucleotide sequence of a DNA fragment.
DNA topo-isomeraseAn enzyme that catalyses the introduction or removal of supercoils in DNA. Synonym: topo-isomerase.
DODesignated Office the national Office or intergovernmental organization of or acting for the Contracting State designated by the applicant under Chapter I…
Dobson UnitUnit used to measure the abundance of ozone in the atmosphere. One Dobson unit is the equivalent of 2.69/ x 1016 molecules of ozone/cm2.
DoldrumsThe regions on either side of the equator where air pressure is low and winds are light.
DollyUnlike the French roulette where the croupier simply points with the stick on the winning number on the table, in the American roulette the croupier uses…
DolomiteA magnesium-rich carbonate sedimentary rock. Also, a magnesium-rich carbonate mineral (CaMgCO3).
DomainA sub-network of servers and computers within a LAN. Domain information is useful when restoring backup tapes, particularly of email.
DomeA structure curved both in the lengthwise and crosswise direction.
Dome (Geodesic)An architectural design invented by Buckminster Fuller with a regular polygonal structure based on radial symmetry.
Dome, volcanicRounded, steep-sided mounds built by very viscous magma, usually either dacite or rhyolite.
Domestic ConsumptionThe quantity, or quantity per capita, of water consumed in a municipality or district for domestic uses or purposes during a given period, generally one…
Domestic Use of waterThe use of water primarily for household purposes, the watering of livestock, the irrigation of gardens, lawns, shrubbery, etc.
Domestic water useWater used for household purposes such as drinking; food preparation; bathing; washing clothes, dishes, and dogs; flushing toilets; and watering lawns and…
Domestic water use (residential water use)Water for household purposes, such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and water lawns and gardens.
DominantAn allele is said to be dominant if it expresses its phenotype even in the presence of a recessive allele. See Allele, Phenotype, Recessive.
Dominant geneA gene whose phenotype is when it is present in a single copy.
dominant marker selectionSelection of cells via a gene encoding a product that enables only the cells that carry the gene to grow under particular conditions.
dominant selectable markerA gene that allows the host cell to survive under conditions where it would otherwise die. Synonym: positive selectable marker.
Dominant(-acting) oncogeneA gene that stimulates cell proliferation and contributes to oncogenesis when present in a single copy. (See Oncogene.)
DonorIn a solar photovoltaic device, an n-type dopant, such as phosphorus, that puts an additional electron into an energy level very near the conduction band…
donor junction siteThe junction between the 5' end of an exon and the 3' end of an intron. See: acceptor junction site.
DopantA chemical element (impurity) added in small amounts to an otherwise pure semiconductor material to modify the electrical properties of the material.
Doppler Effectapparent change in frequency of a wave due to the relative motion of the source and observer.
Doppler RadarRadar that can measure radial velocity, the instantaneous component of motion parallel to the radar beam (i.e., toward or away from the radar antenna).
doppler velocity (m/s)When used, the positive is down (towards the radar). Particle and air motions contribute to the velocity.
DormancyA period in which a plant does not grow, awaiting necessary environmental conditions such as temperature, moisture, nutrient availability.
dosage compensationA regulatory mechanism for sex-linked genes, to allow equivalent levels of gene expression from (in mammals) XY or XX genotypes, even though the gene copy…
doseThe amount of medicine taken, or radiation given, at one time.
dose assessmentThe process by which uptake and dose of a toxic substance are identified and quantified.
dose equivalentAn absorbed dose that is adjusted or weighted to account for the potential of different radiations with the same damage.
double crossing-overThe formation of two chiasmata within a chromosome arm, leading to the generation of a double recombinant gamete with respect to genes located within the…
Double curvature arch damAn arch dam which is curved in plan and elevation, with undercutting of the heel and in most instances, a downstream overhang near the crest.
double fertilizationA process, unique to flowering plants, in which two male nuclei, which have travelled down the pollen tube, separately fuse with different female nuclei…
Double helixDescribes the coiling of the antiparallel strands of the DNA molecule, resembling a spiral staircase in which the paired bases form the steps and the…
double recessiveAn organism homozygous for a recessive allele at each of two loci.
Double Wall Heat ExchangerA heat exchanger in a solar water heating system that has two distinct walls between the heat transfer fluid and the domestic water, to ensure that there…
Double-Pane or Glazed WindowA type of window having two layers (panes or glazing) of glass separated by an air space.
double-stranded DNA(Abbreviation: dsDNA ). Two complementary strands of DNA annealed in the form of a double helix. Synonym: duplex DNA.
doubling time(DUH-bling...) In biology, the amount of time it takes for one cell to divide or for a group of cells (such as a tumor) to double in size.
down promoter mutationA mutation that decreases the frequency of initiation of transcription. This leads to a fall in the level of mRNA compared to the wild type state.
down-regulateTo induce genetically a reduction in the level of a gene's expression.
Down-Valley WindA thermally driven wind directed down a valley's axis, usually occurring during nighttime; part of the along-valley wind system.
DownburstA strong downdraft current of air from a cumulonimbus cloud, often associated with intense thunderstorms.
Downdraft(Abbrev. DWNDFT) - A small-scale column of air that rapidly sinks toward the ground, usually accompanied by precipitation as in a shower or thunderstorm.
Downdraft gasifierA gasifier in which the product gases pass through a combustion zone at the bottom of the gasifier.
Downslope FlowA thermally driven wind directed down a mountain slope and usually occurring at night; part of the along-slope wind system.
downstreamThe region extending in a 3' direction from a gene.
Downstream faceThe inclined surface of a dam away from the reservoir. See face.
downstream processingA general term for biotechnological processes which follow the biology, i.e. fermentation of a micro-organism or growth of a plant.
Downstream SlopeThe slope or face of the dam away from the reservoir water. This slope requires some kind of protection (e.g.
DownwashA deflection of air downward relative to an object that causes the deflection.
downwelling longwave irradianceThe total diffuse and direct radiant energy, at wavelengths longer than approximately 4 µm, that is being emitted downwards.
Downwelling RadiationThe component of radiation directed toward the earth's surface from the sun or the atmosphere, opposite of upwelling radiation.
downwelling shortwave irradianceThe total diffuse and direct radiant energy that comes from some continuous range of directions, at wavelengths between 0.
Downwind Wind TurbineA horizontal axis wind turbine in which the rotor is downwind of the tower.
DownzoningA change in zoning classification to less intensive use and/or development.
DRDiminishing Returns. Used to describe something that reduces slowly over time on consecutive repetitions of the same action.
DraftA signed, written order by which one party (the drawer) instructs another party (the drawee) to pay a specified sum to a third party (the payee), at sight…
Draft DiverterA door-like device located at the mouth of a fireplace chimney flue for controlling the direction and flow of the draft in the fireplace as well as the…
Draft environmental impact statement (DEIS)A draft statement of environmental effects. Section 102 of the National Environmental Policy Act requires a DEIS for all major federal actions.