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Filebox - Biotechnology Dictionary Category: Earth and Environment > Biotechnology Date & country: 13/09/2007, USA Words: 455

TATA box
An adenine- and thymine-rich promoter sequence located 25-30 bp upstream of a gene, which is the binding site of RNA polymerase.

Telomere
The end of a chromosome.

Template
An RNA or single-stranded DNA molecule upon which a complementary nucleotide strand is synthesized.

Termination codon
Any of three mRNA sequences (UGA, UAG, UAA) that do not code for an amino acid and thus signal the end of protein synthesis. Also known as stop codon. (See Codon.)

Terminator region
A DNA sequence that signals the end of transcription.

Tetracycline
An antibiotic that interferes with protein synthesis in prokaryotes.

Thymidine kinase (tk)
An enzyme that allows a cell to utilize an alternate metabolic pathway for incorporating thymidine into DNA. Used as a selectable marker to identify transfected eukaryotic cells.

Ti (tumor-inducing) plasmid
A giant plasmid of Agrobac- terium tumefaciens that is responsible for tumor formation in infected plants. Ti plasmids are used as vectors to introduce foreign DNA into plant cells.

Toxic Substances Control Act (TSCA)
See Environmental Protection Agency.

Trait
See Phenotype.

Transcapsidation
The partial of full coating of the nucleic acid of one virus with a coat protein of a differing virus. See Coat protein.

Transcription
The process of creating a complementary RNA copy of DNA.

Transducing phage
See Transduction.

Transduction
The transfer of DNA sequences from one bacterium to another via lysogenic infection by a bacteriophage (transducing phage).

Transfection
The uptake and expression of a foreign DNA sequence by cultured eukaryotic cells.

Transfer DNA
See T-DNA.

Transfer RNA (tRNA)
See tRNA.

Transformant
In prokaryotes, a cell that has been ge- netically altered through the uptake of foreign DNA. In higher eukaryotes, a cultured cell that has acquired a malignant phenotype. (See Transformation.)

Transformation
In prokaryotes, the natural or induced uptake and expression of a foreign DNA sequence--typically a recombinant plasmid in experimental systems. In higher eukaryotes, the conversion of cultured cells to a malignant phenotype--typically through infection by a tumor virus or transfection with an oncogene. (See Transformant, Transformation efficiency.)

Transformation efficiency
The number of bacterial cells that uptake and express plasmid DNA divided by the mass of plasmid used (in transformants/microgram). (See Transformation.)

Transforming oncogene
A gene that upon transfection converts a previously immortalized cell to the malignant phenotype. (See Oncogene.)

Transgene
See Transgenic.

Transgenic
An organism in which a foreign DNA gene (a transgene) is incorporated into its genome early in de- velopment. The transgene is present in both somatic and germ cells, is expressed in one or more tissues, and is inherited by offspring in a Mendelian fashion. See Transgenic animal, Transgenic plant.

Transgenic animal
Genetically enginnered animal or offspring of genetically engineered animals. The transgenic animal usually contains material from at lease one unrelated organism, such as from a virus, plant, or other animal. See Transgenic.

Transgenic plant
Genetically engineered plant or offspring of genetically engineered plants. The transgenic plant usually contains material from at least one unrelated organisms, such as from a virus, animal, or other plant. See Transgenic.

Transition-state intermediate
In a chemical reaction, an unstable and high-energy configuration assumed by reactants on the way to making products. Enzymes are thought to bind and stabilize the transition state, thus lowering the energy of activation needed to drive the reaction to completion.

Translation
The process of converting the genetic infor- mation of an mRNA on ribosomes into a polypeptide. Transfer RNA molecules carry the appropriate amino acids to the ribosome, where they are joined by peptide bonds.

Translocation
The movement or reciprocal exchange of large-chromosomal segments, typically between two different chromosomes.

Transposable genetic element
See Transposon.

Transposition
The movement of a DNA segment within the genome of an organism.

tRNA (transfer RNA)
The class of small RNA molecules that transfer amino acids to the ribosome during protein synthesis. See Transfer RNA.

Trypsin
A proteolytic enzyme that hydrolyzes peptide bonds on the carboxyl side of the amino acids arginine and lysine.

TSCA
The Toxic Substances Control Act. See Environmental Protection Agency.

Tumor DNA
See T-DNA.

Tumor virus
A virus capable of transforming a cell to a malignant phenotype. (See Virus.)

Tumor-inducing plasmid
See Ti plasmid.

U.S. Department of Agriculture
The U.S. agency responsible for regulation of biotechnology products in plants and animals. The major laws under which the agency has regulatory powers include the Federal Plant Pest Act (PPA), the Federal Seed Act, and the Plant Variety Act (PVA). In addition, the Science and Education (S&E) division has nonregulatory oversight of research activities that the agency funds.

Upstream
The region extending in a 5' direction from a gene.

USDA
See The U.S. Department of Agriculture.

Vaccine
A preparation of dead or weakened pathogen, or of derived antigenic determinants, that is used to induce formation of antibodies or immunity against the pathogen. (See Polyvalent vaccine, Subunit vaccine.)

Vaccinia
The cowpox virus used to vaccinate against smallpox and, experimentally, as a carrier of genes for antigenic determinants cloned from other disease organisms.

Variable surface glycoprotein (VSG)
One of a battery of antigenic determinants expressed by a microorganism to elude immune detection.

Variation
Differences in the frequency of genes and traits among individual organisms within a population.

Vector
An autonomously replicating DNA molecule into which foreign DNA fragments are inserted and then propagated in a host cell. Also living carriers of genetic material (such as pollen) from plant to plant, such as insects.

Viral oncogene
A viral gene that contributes to malig- nancies in vertebrate hosts. (See Oncogene.)

Viroid
A plant pathogen that consists of a naked RNA molecule of approximately 250-350 nucleotides, whose extensive base pairing results in a nearly correct double helix. (See Satellite RNA.)

Virulence
The degree of ability of an organism to cause disease.

Virus
An infectious particle composed of a protein capsule and a nucleic acid core, which is dependent on a host organism for replication. A double-stranded DNA copy of an RNA virus genome that is integrated into the host chromosome during lysogenic infection. (See Coat protein, DNA, Genome, Host, Nucleic acid, RNA, Tumor virus.)

VSG
See Variable surface glycoprotein.

Weed
An undesirable plant.

Weediness
Unwanted effects of a plant.

Wild type
An organism as found in nature; the organism before it is genetically engineered.

X-linked disease
A genetic disease caused by a mutation on the X chromosome. In X-linked recessive conditions, a normal female 'carrier' passes on the mutated X chromosome to an affected son.

X-ray crystallography
The diffraction pattern of X-rays passing through a pure crystal of a substance.

Z-DNA
A region of DNA that is 'flipped' into a lefthanded helix, characterized by alternating purines and pyrimidines, and which may be the target of a DNA-binding protein.