(S T A T s ),

A HERBICIDE

CHEMISTRY,

from the thermophilic bacteria Thermus aquaticus. Commonly utilized to catalyze PCR reactions due to its heat resistance (needed for thermal cycles utilized in the PCR technique). See also DNA POLYMERASE,

POLYMERASE, KILODALTON (Kd), DEOXYRIBONUCLEIC ACID (DNA), BACTERIA, THERMOPHILIC BACTERIA, PCR, POLYMERASE CHAIN REACTION

(PCR) TECHNIQUE.

Target (of a herbicide or insecticide) T h e molecule (receptor, enzyme, etc.) within a weed plant or within a pest insect that a given herbicide or insecticide is “aimed” at (e.g., when scientists are conducting research aimed at creating that herbicide or insecticide). For example, glyphosate-containing herbicides act on the (target) crucial plant enzyme EPSP synthase. For example, insectresistant transgenic plants containing “B.t. gene(s)” act on (target) receptors inside the digestive system of specific insect species via the B.t. protoxin. See also RECEPTORS, ENZYME,

GLYPHOSATE, EPSP SYNTHASE, TRANSGENIC

(ORGANISM), PROTOXIN, HERBICIDE-TOLERANT CROP, PAT GENE, GLUTAMINE, GLUTAMINE SYNTHETASE, CORN, BIOLOGICAL ACTIVITY, TARGET-

LIGAND INTERACTION SCREENING.

Target (of a therapeutic agent) T h e m o l e - cule (receptor) or moiety that a given drug or therapeutic regimen (e.g., gene delivery) is “aimed” at (i.e., when scientists are working to create/discover that drug or regimen). Targets can be normally occurring constituents of the body (receptors, enzymes, factors, hormones, ion channels, nuclear receptors, DNA, etc.), nonnormal constituents of the body (tumors, antigens on tumor surfaces, etc.), or (external, invading) pathogenic agents

T(microorganisms, viruses, parasites, etc.). See

also ENZYME, FACTOR, HORMONE, ION CHANNELS,

NUCLEAR RECEPTORS, DEOXYRIBONUCLEIC ACID

(DNA), TUMOR, MICROORGANISM, BIOLOGICAL

ACTIVITY, PATHOGEN, PATHOGENIC, VIRUS, PHAR-

MACOPHORE, GENE DELIVERY, RECEPTORS, MOIETY,

COMBINATORIAL CHEMISTRY, COMBINATORIAL

BIOLOGY, SIGNALING, SIGNAL TRANSDUCTION,

G-PROTEINS , TUMOR NECROSIS FACTOR (TNF),

HIGH-THROUGHPUT SCREENING (HTS), TARGET-

LIGAND INTERACTION SCREENING, BIOCHIPS.

Target-Ligand Interaction Screening A methodology of high-throughput screening (HTS)

that is utilized to screen a large number of candidates (e.g., compounds) based upon their interaction (e.g., chemical “binding”) to a preselected “target” (e.g., molecule present within a cell membrane, molecule placed on a biochip or other bioassay to facilitate HTS, molecule present on the surface of a nematode utilized in HTS, etc.).

See also HIGH-THROUGHPUT SCREENING (HTS),

TARGET (OF A THERAPEUTIC AGENT), TARGET (OF

OR INSECTICIDE), COMBINATORIAL

COMBINATORIAL BIOLOGY, LIGAND

(IN BIOCHEMISTRY), RECEPTORS, SIGNAL TRANSDUCTION, NUCLEAR RECEPTORS, BIOCHIP, SIGNAL TRANSDUCERS AND ACTIVATORS OF TRANSCRIP- T I O N C A E N O R H A B D I T I S E L E G A N S

(C. ELEGANS).

TAT The name of a protein that helps the HIV (“AIDS virus”) to cross the human cell plasma membrane, thereby enabling infection of those cells by HIV (human immunodeficiency virus). TAT is the main activator of HIV gene expression in cells; it is a protein which complexes with TAR (a 60-nucle- otide sequence found in all viral messenger ribonucleic acid) to mediate synthesis of proteins (in an infected cell) necessary for HIV to reproduce. See also TATA HOMOLOGY,

HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 (HIV- 1),

HUMAN IMMUNODEFICIENCY VIRUS TYPE 2

(HIV- 2), GENE, EXPRESS, NUCLEOTIDE, MESSEN-

GER RNA (mRNA), VIRUS, PROTEIN, PLASMA MEM-

BRANE, CELL.

TATA Homology An adenine-thymidine-rich (gene) sequence present 20–30 nucleotides “upstream” of the transcription start site on most eucaryotic protein coding genes; it is required for correct expression. Recent research indicates that blocking this portion of the (gene) sequence may inhibit ability of the AIDS virus to reproduce. See also GENE,

GENETIC CODE, NUCLEOTIDE, ADENINE, SEQUENCE

(OF A DNA MOLECULE), TAT, TRANSCRIPTION,

STARTPOINT, EUCARYOTE, CODING SEQUENCE,

HOMOLOGY, PRIBNOW BOX, PROMOTER, SEQUENCE

(OF A PROTEIN MOLECULE).

Taxol A phytochemical that is naturally produced in some plants and functions to protect those plants from the plant pathogen known as water mold. Coined during the 1960s by Monroe E. Wall when it was originally

© 2002 by CRC Press LLC

isolated from the Pacific yew tree (genus Taxus), Taxol™ is now a trademark of the Bristol-Myers Squibb Co. refering to the antitumor pharmaceutical sold by the company. The active compound from Pacific yew tree is now known as paclitaxel. Both Taxol™ and paclitaxel act by binding and stabilizing microtubules in cells (thereby halting/preventing the uncontrolled cell growth/proliferation that is cancer). See also

CHEMOTHERAPY, PACLITAXEL, CANCER, CELL,

MICROTUBULES, TUBULIN.

TBT Acronym for the Technical Barriers to Trade (TBT) Agreement to WTO. See also

TECHNICAL BARRIERS TO TRADE (TBT) AGREEMENT,

WORLD TRADE ORGANIZATION (WTO).

TCGF See T CELL GROWTH FACTOR (TCGF).

TCK Smut See TELETHIA CONTROVERSIA KOON

SMUT.

Technical Barriers To Trade (TBT) Agreement The agreement to GATT/WTO, via which WTO member nations agreed to base their import (restrictive) regulations and standards (e.g., mandatory packaging, package marking, testing, certification, labeling requirements, etc.) — known as TBT measures — only on scientific assessments of actual risks (i.e., for those TBT measures intended to protect human health, animal and plant health, or the environment) and to require only those TBT measures that do not create unnecessary obstacles to international

trade. See also WORLD TRADE ORGANIZATION

(WTO), SPS, SANITARY AND PHYTOSANITARY (SPS)

AGREEMENT, SANITARY AND PHYTOSANITARY

(SPS) MEASURES, TECHNICAL BARRIERS TO TRADE

(TBT MEASURES).

Technical Barriers To Trade (TBT) Measures These are (restrictive) import regulations and standards (e.g., mandatory pack- a g i n g , p a c k a g e m a r k i n g , t e s t i n g , certification and labeling requirements, etc.). Some of them are designed to protect human health, animal and plant health, and/or the environment. In the Technical Barriers to Trade (TBT) Agreement to GATT/WTO, the WTO member nations agreed to base their TBT measures only on requirements that do not create unnecessary obstacles to international trade. See also TECHNICAL BARRIERS TO

TRADE (TBT) AGREEMENT, SPS, WORLD TRADE

ORGANIZATION (WTO).

Technology Protection System See CESSATION

CASSETTE.

Telethia Controversia Koon Smut A f u n g a l disease that sometimes afflicts wheat (Triticum aestivum) plants. See also FUNGUS, WHEAT.

Telomerase An enzyme that enables the “repair” of telomeres (thereby stabilizing their length, and preventing “shortening” of the telomeres). The telomerase enzyme is only present in cancerous cells (thereby enabling the “immortality” of cancerous cells). Human telomerase contains an RNA component and a catalytic-protein component (i.e., a member of the reverse transcriptase “family” of enzymes). See also REVERSE

TRANSCRIPTASES, CANCER, NEOPLASTIC GROWTH,

ZYGOTE, TELOMERES, ENZYME, ONCOGENES,

HYBRIDOMA, MONOCLONAL ANTIBODIES (MAb),

AGING.

Telomeres DNA sequences, that do not code for proteins, which are located at the (end) tips of chromosomes. Telomeres consist of the sequence GGGGTT repeated many times. With the exception of certain types of cells (e.g., zygotes, cancerous cells, “immortal” hybridoma cells), portions of each telomere “break off “ each time the cell containing that chromosome divides. This “shortening” process serves to limit the lifetime (i.e., number of replications) of those (noncancerous, nonzygote, nonhybridoma,

etc.) cells. See also DEOXYRIBONUCLEIC ACID

(DNA), CODING SEQUENCE, PROTEIN, CHROMO-

SOMES, SEQUENCE (OF A DNA MOLECULE), TELOM-

ERASE, MITOSIS, MITOGEN, CANCER, GAMETE,

AGING, RETINOIDS, HYBRIDOMA, ZYGOTE.

Template In general terms, it is a mold or pat- T tern that can be copied or its shape repro-

duced. When used with reference to molecular dimensions, it is a macromolecular mold or pattern for the synthesis of another macromolecule. See also DEOXYRIBO-

NUCLEIC ACID (DNA), STRUCTURAL GENE, INFOR-

M A T I O N A L M O L E C U L E S , H E R E D I T Y, G E N E ,

GENETIC CODE, GENETIC MAP, BIOSENSORS

(CHEMICAL), GENOSENSORS, RIBONUCLEIC ACID

(RNA), GENE REPAIR (DONE BY MAN), CODON,

EXON, CHIMERAPLASTY, NANOTECHNOLOGY,

PRIMER (DNA).

© 2002 by CRC Press LLC

THERMO-

Teosinte A wild plant (Zea diploperennis), native to the country of Mexico, which is related to (domesticated) corn/maize (Zea mays L.). See also CORN, WILD TYPE.

Termination Codon Also known as terminator sequence. One of three triplet sequences (U-A-G, U-A-A, or U-G-A) found in DNA molecules (genes) that cause termination of protein synthesis; they are also called nonsense codons. The sequences cause the termination of the peptide chain and its release in free form. See also CODING SEQUENCE,

C O D O N , D E O X Y R I B O N U C L E I C A C I D (D N A ),

GENETIC CODE, NONSENSE CODON, SEQUENCING

(OF DNA MOLECULES), CONTROL SEQUENCES.

Terminator See TERMINATION CODON.

Terminator Cassette See CESSATION CASSETTE. Terminator Sequence See TERMINATION CODON.

Tertiary Structure The three-dimensional folding of the polypeptide (i.e., protein) molecular chains that characterizes a protein molecule in its native state. See also PROTEIN

STRUCTURE, PROTEIN, POLYPEPTIDE (PROTEIN),

CONFORMATION, PROTEIN FOLDING, NATIVE CON-

FORMATION, PROTEOMICS, TRANSCRIPTOME.

Testosterone An androgen (steroid hormone) that is biochemically synthesized (made) from androstenedione, which is itself synthesized from progesterone. Testosterone is responsible for the development of male secondary sex characteristics in humans such as greater strength, larger body size, facial hair, a deeper voice, etc. See also STEROID, ESTROGEN.

Tetrahydrofolic Acid The reduced, active coenzyme form of the vitamin folic acid; involved in C1 transfers. Tetrahydrofolate (also known as FH4) serves as an intermediate carrier (molecule) of methyl, hydroxy-

Tmethyl, or formyl groups (all containing one carbon atom) in a relatively large number of enzymatic reactions in which such one-car- bon groups are transferred from one metabolite to another.

TG See TRIGLYCERIDES.

TGA The government regulatory agency charged with approving all pharmaceutical products sold within Australia. See also FOOD

AND DRUG ADMINISTRATION (FDA), KOSEISHO,

COMMITTEE FOR PROPRIETARY MEDICINAL PROD-

UCTS (CPMP), EUROPEAN MEDICINES EVALUATION

AGENCY (EMEA), MEDICINES CONTROL AGENCY

(MCA), COMMITTEE ON SAFETY IN MEDICINES,

BUNDESGESUNDHEITSAMT (BGA), GENE TECHNOL-

OGY OFFICE.

TGF See TRANSFORMING GROWTH FACTOR-ALPHA

(TGF-ALPHA), TRANSFORMING GROWTH FACTOR-

BETA (TGF-BETA).

Thale Cress Common name for Arabidopsis

thaliana. See also ARABIDOPSIS THALIANA.

Thermoduric An organism that can survive high temperatures but does not necessarily grow at such temperatures. See also THERMO-

PHILE, MESOPHILE, EXTREMOPHILIC BACTERIA,

PSYCHROPHILE.

Thermophile An organism whose optimum temperature for growth is close to, or exceeds, the boiling point of water (100°C,

212°F). See also EXTREMOPHILIC BACTERIA,

THERMOPHILIC BACTERIA, THERMODURIC, MESO-

PHILE, PSYCHROPHILE, EUCARYOTE.

Thermophilic Bacteria Literally “heat loving” bacteria. They are a category of thermophiles generally found near geothermal vents beneath bodies of water. See also

PHILE, THERMODURIC, EXTREMOPHILIC BACTERIA,

MESOPHILE, PSYCHROPHILE.

Thioesterase A “family” of enzymes naturally produced within some plants, such as the California bay tree (Umbellularia californica). Thioesterase catalyzes those plants’ production of the fatty acid laurate. See also FATS,

FATTY ACID, LAUROYL-ACP THIOESTERASE,

ENZYME, LAURATE, CANOLA, HIGH-LAURATE

CANOLA.

Thiol Group Refers to a specific chemical entity (on a molecule). See also CYSTEINE

(cys), CYSTINE.

Thioredoxin See ALLERGIES (FOODBORNE).

Threonine (thr) A crystalline, α-amino acid considered essential for normal growth of animals. It is biosynthesized (made) from aspartic acid and is a precursor of isoleucine in microorganisms. See also ESSENTIAL AMINO

ACIDS.

Thrombin The key to thrombus (blood clot) formation. Thrombin is a proteolytic enzyme that cleaves fibrinogen into (molecular) pieces, which then spontaneously assemble themselves into fibrin, which forms a clot. See

also THROMBUS, THROMBOSIS, THROMBOMODULIN, THROMBOLYTIC AGENTS, FIBRIN, FIBRINOLYTIC

AGENTS, CASCADE.

© 2002 by CRC Press LLC

PATHWAY,

THROMBIN,

Thrombolytic Agents Bloodborne compounds (such as tissue plasminogen activator) that work to disintegrate (break up or lyse) blood

clots. See also FIBRIN, FIBRINOLYTIC AGENTS,

TISSUE PLASMINOGEN ACTIVATOR (tPA).

Thrombomodulin A cell surface protein found on endothelial cells that plays a key role in modulating the final step in the coagulation process. After thrombin binds to thrombomodulin, thrombin loses its ability to cleave fibrinogen to form fibrin. In addition, once thrombin binds to thrombomodulin, thrombin’s activation of protein C is increased 200-fold and this activated protein C then degrades factors Va and VIIIa which are both required for the production of thrombin from prothrombin. Hence, thrombomodulin modulates the activity of the enzyme thrombin causing a cessation of fullblown clotting activity. See also

PROTEIN, PROTEIN C, THROMBOSIS,

PATHWAY FEEDBACK MECHANISMS.

Thrombosis The intravascular (i.e., inside of blood vessel) formation of a blood clot. See

also THROMBIN, THROMBUS, THROMBOLYTIC

AGENTS, TRIGLYCERIDES, FIBRIN, FIBRINOLYTIC

AGENTS, TISSUE PLASMINOGEN ACTIVATOR (tPA).

Thrombus The blood clot itself. The mass of blood coagulated in situ in the heart or other blood vessel. For example, such a clot causes a heart attack when the coagulation occurs in the vessels feeding the heart. See also

T H R O M B I N , T H R O M B O S I S , T H R O M B O L Y T I C

AGENTS, FIBRIN, TRIGLYCERIDES, FIBRINOLYTIC

AGENTS.

Thymine (thy) A pyrimidine component of nucleic acid first isolated from the thymus. Its hydrogen-bonding counterpart in RNA is

uracil. See also NUCLEIC ACIDS, PYRIMIDINE,

BASE (NUCLEOTIDE), THYMUS, RIBONUCLEIC ACID

(RNA).

Thymoleptics A class of drugs that primarily exerts its effect on the brain influencing “feeling” and behavior.

Thymus A gland that enables cells of the immune system of mammals to mature. In humans, it lies behind the breast bone and extends upward as far as the thyroid gland. The thymus is the place in the body where T lymphocytes are “taught” to distinguish foreign (e.g., pathogen) antigens from “self”

cell antigens, to avoid immune responses in which the body’s immune system attacks organs and other cells within the body (resulting in autoimmune diesease). Any T lymphocytes that remain “autoreactive” (i.e., would tend to attack “self” cells, such as organs in the body) are destroyed by the thymus via a cytotoxic mechanism.

	An example of an autoimmune disease is
	multiple sclerosis (MS), where the body’s
	acetylcholine receptors are attacked by the
	body’s immune system. Since acetylcholine
	is crucial in the transmission of nerve
	impulses to the body’s muscles, such
	destruction of acetylcholine receptors results
	in loss of control of the body’s muscles. See
	also T LYMPHOCYTES, CYTOTOXIC, RECEPTORS,
	T CELLS , IMMUNE RESPONSE, PATHOGEN, ANTIGEN,
	NEUROTRANSMITTER, ACETYLCHOLINE, AUTO-
	IMMUNE DISEASE.
	Thyroid Gland A gland that is found on both
	sides of the trachea (“windpipe”) in humans.
	This gland secretes the hormone thyroxine,
	which increases the rate of metabolism. See
	also THYROID STIMULATING HORMONE (TSH),
	GRAVE’S DISEASE.
	Thyroid Stimulating Hormone (TSH) A hor-
	mone that causes the thyroid gland to secrete
	additional amounts of thyroxine. See also
	THYROID GLAND, GRAVE’S DISEASE.
	Ti Plasmid Abbreviation for tumor-inducing
	plasmid or tumor induction plasmid. It is the
	plasmid of Agrobacterium tumefaciens bac-
	teria that naturally has part of its DNA trans-
	ferred to a plant when Agrobacterium
	tumefaciens infects that plant (e.g., via a
	wound in the plant). After it has been trans-
	ferred into the plant, that Ti plasmid DNA
		T
	segment (now known as T-DNA or trans-
	ferred DNA) inserts itself into the plant’s
	DNA, where it causes cells to grow into
	tumor-like structures known as galls. The Ti
	plasmid can be modified so that it can be
	utilized (by genetic engineers) to insert
	genes from other organisms into plants. See
	also PLASMID, BACTERIA, AGROBACTERIUM TUME-
	FACIENS, CELL, DEOXYRIBONUCLEIC ACID (DNA),
	GENE, GENETIC ENGINEERING.
	Tissue Culture The growth and maintenance
	(by researchers) of cells from higher organ-
	isms in vitro, i.e., in a sterile test tube or petri

© 2002 by CRC Press LLC