transcriptional anti-terminatorA protein that prevents RNA polymerase from terminating transcription at specific transcription termination sequences.
transcriptional roadblockA DNA -binding protein which affects the rate at which RNA polymerases transcribe genes.
TranscriptomeThe full complement of activated genes, mRNAs, or transcripts in a particular tissue at a particular time
TransdifferentiationThe ability of a particular cell of one tissue, organ or system, including stem or progenitor cells, to differentiate into a cell type characteristic of…
transferaseA class of enzymes that catalyses the transfer of a group of atoms from one molecule to another.
TransformantIn prokaryotes, a cell that has been ge- netically altered through the uptake of foreign DNA.
transformation(TRANZ-for-MAY-shun) In medicine, the change that a normal cell undergoes as it becomes malignant.
Transformation efficiencyThe number of bacterial cells that uptake and express plasmid DNA divided by the mass of plasmid used (in transformants/microgram). (See Transformation.)
transformation efficiency or frequencyThe fraction of a cell population that takes up and integrates the introduced transgene; expressed as the number of transformed cells recovered divided by…
Transforming oncogeneA gene that upon transfection converts a previously immortalized cell to the malignant phenotype. (See Oncogene.)
transgenesisThe introduction of a gene or genes into animal or plant cells, which leads to the transmission of the input gene (transgene ) to successive generations.
TransgenicAn organism in which a foreign DNA gene (a transgene) is incorporated into its genome early in de- velopment.
Transgenic animalGenetically enginnered animal or offspring of genetically engineered animals. The transgenic animal usually contains material from at lease one unrelated…
Transgenic plantGenetically engineered plant or offspring of genetically engineered plants. The transgenic plant usually contains material from at least one unrelated…
transgressive variationThe appearance, in a segregating generation, of individuals showing expression of a trait outside the extremes defined by the parent of the cross that was…
transient expressionShort-term activity of a transgene following its introduction into. Transient expression usually implies non-integration of the transgene into the.
transitionThese are where one type of bottom material or structure changes to another, for instance, a rock pile to solid rock, or sand to gravel.
transition stageThe period between juvenile and reproductive stages of growth.
Transition-state intermediateIn a chemical reaction, an unstable and high-energy configuration assumed by reactants on the way to making products.
TranslationThe process of converting the genetic infor- mation of an mRNA on ribosomes into a polypeptide.
Translocation(TRANZ-loh-KAY-shun) A genetic change in which a piece of one chromosome breaks off and attaches to another chromosome.
Transplantation(tranz-plan-TAY-shun) The replacement of tissue with tissue from the person's own body or from another person.
Transplantation biologyThe science that studies the transplantation of organs and cells. Transplantation biologists investigate scientific questions to understand why foreign…
Transposable elementA class of DNA sequences that can move from one chromosomal site to another.
transposon taggingA method of gene isolation that exploits the disruption of normal gene expression that is the result of an insertion of a transposon within, or close to…
transversionThe substitution in DNA or RNA of one purine by a pyrimidine or vice versa. See: transition, base substitution.
tri-hybridThe hybrid offspring of a cross between parents carrying contrasting alleles at three loci.
tribrid proteinA fusion protein that has three segments, each encoded by parts of different genes.
trichomeA short filament of cells, resulting in a hair-like structure.
trinucleotide repeatTandem repeats of three nucleotides that are present in many genes. Commonly trinucleotide repeats have undergone variable expansion in copy number…
tripartite matingA process in which conjugation is used to transfer a plasmid vector to a when the plasmid vector is not self-mobilizable.
tripletA sequential group of three nucleotides in DNA or RNA. See: codon.
triploidA cell, tissue or organism containing three times the haploid number of chromosomes.
trisomyThe presence in a diploid cell or organism of an extra chromosome of one homologue (chromosome formula: 2n + 1). See: disomy; monosomic.
triticaleThe hybrid man-made species formed by the crossing of tetraploid or hexaploid wheat with diploid rye.
tRNAAbbreviation for transfer RNA. Small RNA molecules that transfer amino acids to the ribosome during protein synthesis.
tRNA (transfer RNA)The class of small RNA molecules that transfer amino acids to the ribosome during protein synthesis. See Transfer RNA.
Trophectoderma term used to refer to trophoblast cells in mice.
Trophoblast(TROH-foh-BLAST) A thin layer of cells that helps a developing embryo attach to the wall of the uterus, protects the embryo, and forms a part of the…
tropismPlant response to an external stimulus, resulting in the bending/turning of stem or root growth.
true-to-typeConforming to the phenotype of the breed/variety.
TrypsinA proteolytic enzyme that hydrolyzes peptide bonds on the carboxyl side of the amino acids arginine and lysine.
trypsin inhibitorSubstances inactivating trypsin, typically found in of certain plants, where they are thought to have evolved as anti-feedant agents against insect…
TSCAThe Toxic Substances Control Act. See Environmental Protection Agency.
TTPAbbreviation for thymidine 5'-triphosphate. TTP is required for DNA synthesis since it is a direct precursor molecule. See: thymidine, thymidylic acid.
tubulin(TOO-byuh-lin) One of a group of proteins found in high levels in the cell cytoplasm (fluid inside a cell but outside the cell's nucleus).
tumble tubeA glass tube mainly used in vitro to agitate and consequently aerate suspension cultures.
tunicaThe outer one- to four-cell layer region of the apical meristem, where cell division is anticlinal, i.e. perpendicular to the surface.
turbidostatAn open continuous culture in which a pre-selected biomass density is uniformly maintained by automatic removal of excess cells.
turgidSwollen, distended; referring to a cell that is extended as a result of adequate water uptake. Loss of turgidity in plant cells is a sign of water deficit.
turgor pressureThe pressure within a cell resulting from the absorption of water into the vacuole and the imbibition of water by the protoplasm.
turionAn underground bud or shoot from which an aerial stem arises. See: sucker.
twinOne of two individuals originating from the same zygote.
TwinningDevelopment of monozygotic twins, that is, when a very early embryo separates into two pieces, each of which continues development, so that two embryos…
Type-1A diabetesA form of insulin dependent diabetes, usually becoming evident in childhood, resulting from an autoimmune reaction that destroys the pancreatic beta…
U.S. Department of AgricultureThe U.S. agency responsible for regulation of biotechnology products in plants and animals.
ubiquitinA small protein, present in all eukaryotic cells, which plays an important role in tagging proteins destined for proteolytic cleavage (because they are…
Umbilical cord blood stem cellsstem cells collected from the umbilical cord at birth that can produce all of the blood cells in the body (hematopoietic).
Umbilical cord stem cellsHematopoietic stem cells are present in the blood of the umbilical cord during and shortly after delivery.
UMPAbbreviation for the (ribo)nucleotide uridine 5'-monophosphate. See: uridylic acid.
understockHost plant for a grafted scion, a branch or shoot from another plant; an understock may be a fully grown tree or a stump with a living root system.
UndifferentiatedA term used to describe cells or tissues that do not have specialized ("mature") structures or functions.
unencapsidatedA virus not enclosed by a coat protein or capsid.
unequal crossing overAbnormal meiotic event, in which one chromatid contains a duplication and the other a deletion.
unicellularTissues, organs or organisms consisting of a single cell.
uniparental inheritanceThe inheritance of genes exclusively from one parent, e.g. chloroplast DNA is inherited either maternally (many angiosperms) or paternally (most…
UnipotentRefers to a cell that can only develop in a specific way to produce a certain end result.
Unipotent stem cellsStem cells that self-renew as well as give rise to a single mature cell type; e.g., spermatogenic stem cells.
unisexualHigher organisms (animals or plants) possessing either male or female reproductive organs, but not both.
univalentAn unpaired chromosome at the first division of meiosis.
universal donor cellCells that, after introduction into a recipient, will not induce an immune response that leads to their rejection.
universalityReferring to the genetic code, the triplet codon s are translated to the same amino acid, with minor exceptions, in virtually all species.
unorganized growthIn vitro formation of tissues with few differentiated cell types and no recognizable structure; typical structure of calli formed in tissue culture.
upstreamThe region extending in a 5' direction from a gene.