stamenFloral structure made up of an anther and a filament. The stamen is the male organ of a flower.
Standard deviationStandard deviation is a statistical measurement of how far a variable quantity, such as the price of a stock, moves above or below its average value.
standard errorThe standard error of an estimate is a measure of the sampling variability of the estimate.
starchA substance found in plants. It contains sugar molecules joined chemically. It is found in high levels in foods such as potatoes, rice, corn, and wheat.
StarLinkTMAn insect-resistant variety of corn that was approved for animal feed only, not labeled for human consumption.
start codonThe codon which specifies the first amino acid of a polypeptide chain and at which the ribosome starts the process of translation.
Stationary phaseThe plateau of the growth curve after log growth, during which cell number remains constant. New cells are produced at the same rate as older cells die.
steady stateIn a continuous fermentation process, the condition under which the number of cells removed with the outflow is exactly balanced by the number of newly…
steleThe central vascular cylinder, inside the cortex, of roots and stems of higher plants.
stemThe main body of the above-ground portion of a tree, shrub, herb or other plant; the ascending axis, whether above or below ground, of a plant.
Stem cellA cell from which other types of cells develop. For example, blood cells develop from blood-forming stem cells.
sterile(STER-il) Unable to produce children. Also means free from germs.
sterile roomDedicated space for the carrying out of activities that require sterile conditions.
sterilityComplete or partial failure of an individual to produce functional gametes or viable zygotes under a given set of environmental conditions.
sterilize1. The elimination of micro-organisms, using heat, irradiation, filtration or chemicals. 2.
Steward bottleFlask developed for the growth of cells and tissues in a liquid medium, in which they can be periodically submerged during rotation.
Sticky endA protruding, single-stranded nucleotide se- quence produced when a restriction endonuclease cleaves off center in its recognition sequence.
stigmaReceptive portion of the style, to which pollen adheres.
stirred-tank fermenterA growth vessel in which cells or micro-organisms are mixed by mechanically-driven impellers.
stockA share of stock that represents ownership in the company that issues it. The price of the stock goes up and down, depending on how the company performs…
stock plantThe source plant from which cuttings or explants are obtained. Stock plants should be well maintained to optimize explant and cutting quality.
stock solutionPre-prepared solution of commonly used reagents.
StolonA lateral stem that grows horizontally along the ground surface. Used by some plant species as a mechanism for dispersal, since stolon nodes can…
stoma(STOH-muh) A surgically created opening from an area inside the body to the outside.
stomatal complexIncludes the stoma, together with its guard cells and, when present, any related subsidiary cells.
stomatal indexA measurement of the surface density of stoma ta. This parameter has been found useful in comparing leaves of different sizes.
StratificationLayering of a lake, by temperature, during warmer seasons.
streptavidinA small bacterial protein that binds with high affinity to the vitamin biotin. This streptavidin-biotin combination can be used to link molecules such as…
StressThe response of the body to physical, mental, or emotional pressure. This may make a person feel frustrated, angry, or anxious, and may cause unhealthy…
stress protein(... PROH-teen) One of a group of proteins that help protect cells from stresses such as heat, cold, and low amounts of oxygen or glucose (sugar).
StringencyReaction conditions--notably temperature, salt, and pH--that dictate the annealing of single-stranded DNA/DNA, DNA/RNA, and RNA/RNA hybrids.
Stringent plasmidA plasmid that only replicates along with the main bacterial chromosome and is present as a single copy, or at most several copies, per cell. (See plasmid.
Stroma(stro' mah) the supporting tissue or matrix of an organ; as distinguished from the functional part of the organ.
structural geneA gene that encodes a polypeptide, with either enzymatic or structural functions, and that is required for the normal metabolism and growth of a cell or…
Structure-functionalismThe scientific tradition that stresses the relationship between a physical structure and its function, for example, the related disciplines of anatomy and…
styleSlender column of tissue that arises from the top of the ovary and terminates in the stigma, and through which the pollen tube must grow to achieve…
sub-cloneA procedure in which a large cloned DNA molecule is divided into smaller fragments, each one of which is then separately cloned.
sub-cultureDivision and transfer of a portion of a culture to fresh medium. Sometimes used to denote the adding of fresh liquid to a suspension culture.
sub-culture numberThe number of times cells, etc., have been sub-cultured..
sub-strainDerived from a strain by the isolation of an individual or group of individuals having properties or markers not shared by the strain as a whole.
sub-unit vaccineOne or more immunogenic protein s, either purified from the pathogen itself or produced from a cloned pathogen gene.
SubcloningThe process of tranferring a cloned DNA fragment from one vector to another. (See Cloning.)
subgenomic promoterA promoter added to a virus for a specific heterologous gene, resulting in the formation of mRNA for that gene alone.
subspeciesPopulation(s) of organisms sharing certain characteristics that are not present in other populations of the same species.
Substrate1. A compound that is altered by an enzyme. 2. Food source for growing cells or micro-organisms. 3. Material on which a sedentary organism lives and grows.
Subunit vaccineA vaccine composed of a purified antigenic determinant that is separated from the virulent organism. (See Vaccine, Enzyme.)
suckerA shoot that arises from an underground root or stem. Of particular significance to grafted plants, since the sucker will be genotypically rootstock…
suckeringType of vegetative propagation where lateral buds grow out to produce an individual that is a clone of the parent.
superbugJargon for a particular engineered strain of Pseudomonas, in which various hydrocarbon-degrading genes, derived from different plasmids, were combined…
supercoilThe conformation of a double-stranded DNA molecule placed under torsional stress as a result of interactions with protein s.
Supercoiled plasmidThe predominant in vivo form of plasmid, in which the plasmid is coiled around histone-like proteins.
SupergeneA group of neighboring genes on a chromosome that tend to be inherited together and sometimes are functionally related.
SupernatantThe soluble liquid &action of a sample after centrifugation or precipitation of insoluble solids.
suppressor mutationA mutation that reverses the effect of an earlier mutation, e.g. a mutation in a gene for a tRNA that permits it to read and override an amber mutation.
suppressor-sensitive mutantAn organism that can grow in the presence, but not in the absence of a second genetic factor (the suppressor).
susceptibleInability to withstand injury due to biotic or. Opposite: resistance, tolerance.
suspension cultureA type of culture in which cells and/or clumps of cells grow and multiply while suspended in a liquid medium.
symbiontAn organism living in symbiosis with another, dissimilar organism.
SymbiosisThe close association of two or more dissimilar organisms where both receive an advantage from the association. See Commensalism, Parasitism.
sympatric speciationThe evolution of new species by population s that inhabit the same or overlapping geographic regions.
sympodialA type of plant development in which the terminal bud of the stem stops growing due either to its abortion, or to its differentiation into a floral…
SynapsisThe pairing of homologous chromosome pairs during prophase of the first meiotic division, when crossing over occurs.
synaptonemal complex(Abbreviation: SC). A ribbon-like protein aceous structure formed between paired homologous chromosome s at the end of the first meiotic prophase.
synchronous cultureA culture in which the cell cycle is synchronized for the majority of the cells present.
syncytiumA large cell-like structure formed by the joining together of two or more cells. The plural is syncytia.
syndrome(SIN-drome) A set of symptoms or conditions that occur together and suggest the presence of a certain disease or an increased chance of developing the…
synergidOne of the two haploid nuclei at the micropylar end of the embryo sac of higher plants. The third nucleus is the egg.
synergismAn interaction between two organisms (e.g. Rhizobium and legumes) in which the growth of one is helped by the other. Opposite: antagonism.
T cellOne type of white blood cell that attacks virus-infected cells, foreign cells, and cancer cells.
T cell receptorAn antigen -binding protein, located on the surface of mammalian killer T cells, which mediates the cellular immune response.
T lymphocyteOne type of white blood cell that attacks virus-infected cells, foreign cells, and cancer cells.
T-cell-mediated (cellular) immune responseThe synthesis of antigen-specific T cell receptors and the development of killer T cells in response to an encounter of immune system cells with an…
T-DNAThe DNA segment of the Ti plasmid, present in pathogenic Agrobacterium tumefaciens, that is transferred to plant cells and inserted into the plant's DNA…
T0, T1 and T2Successive generations of plants following a transformation event. The parent transformed plant is T0, its immediate progeny is T1, and the progeny of the…
T4 DNA ligaseAn enzyme, present in bacteria infected with bacteriophage T4, which catalyses the joining (ligation ) of, and repairs nicks in, duplex DNA molecules.
tailingThe in vitro addition, to the 3'-hydroxyl ends of a double-stranded DNA molecule, of multiple copies of a single nucleotide by the enzyme terminal…
tandem repeatTwo (or more) contiguous identical DNA sequences. The orientation can be either head-to-tail, or head-to-head.
tank bioreactorA fermentation vessel designed to grow large scale quantities of a micro-organism (bacteria, yeast or fungi).
tap rootRoot system in which the primary root has a much larger diameter than any lateral roots (e.g. carrot). Opposite: fibrous root.
Taq polymeraseA heat-stable DNA polymerase isolated from the bacterium Therrnus aquaticus, used in PCR. (See Polymerase.)
TargetIn diagnostic tests, the molecule or nucleic acid sequence assayed in a sample.
target site duplicationA short sequence of DNA duplicated when a transposable element inserts at a new locus; usually found at each end of the insertion.
targeted drug deliveryA method of delivering the activated form of a drug molecule to the site in the body where it is needed, rather than allowing it reach the target by…
targeting vectorA cloning vector carrying a DNA sequence capable of participating in a recombinational event at a specified chromosomal location in the host cell.