Biotechnology

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). Tar-
gets can be normally occurring constituents
of the body (receptors, enzymes, factors, hor-
mones, ion channels, nuclear receptors, DNA,
etc.), nonnormal constituents of the body
(tumors, antigens on tumor surfaces, etc.), or
(external, invading) pathogenic agents
(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 meth-
odology 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 sur-
face of a nematode utilized in HTS, etc.).
See also 
HIGH
-
THROUGHPUT SCREENING
  (
HTS
),
TARGET
 (
OF A THERAPEUTIC AGENT
),
TARGET
 (
OF
A HERBICIDE OR INSECTICIDE
),
COMBINATORIAL
CHEMISTRY
,
COMBINATORIAL BIOLOGY
,
LIGAND
(
IN BIOCHEMISTRY
),
RECEPTORS
,
SIGNAL TRANS-
DUCTION
,
NUCLEAR RECEPTORS
,
BIOCHIP
,
SIGNAL
TRANSDUCERS AND ACTIVATORS OF TRANSCRIP-
T I O N
  (
S T A T
s
),
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 infec-
tion of those cells by HIV (human immun-
odeficiency virus). TAT is the main activator
of HIV gene expression in cells; it is a pro-
tein 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
 (
m
RNA
),
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 pro-
duced 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

T
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 com-
pany. 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) Agree-
ment The agreement to GATT/WTO, via
which WTO member nations agreed to base
their import (restrictive) regulations and
standards (e.g., mandatory packaging, pack-
age marking, testing, certification, labeling
requirements, etc.) — known as TBT mea-
sures — 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) Mea-
sures These are (restrictive) import regula-
tions 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 interna-
tional 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 (Triti-
cum 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
  (
MA
b
),
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, “immor-
tal” hybridoma cells), portions of each
telomere “break off “ each time the cell con-
taining that chromosome divides. This
“shortening” process serves to limit the life-
time (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-
tern that can be copied or its shape repro-
duced. When used with reference to
molecular dimensions, it is a macromolecu-
lar 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

T
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 termina-
tor 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 non-
sense codons. The sequences cause the ter-
mination of the peptide chain and its release
in free form. See also 
CODING SEQUENCE
,
CODON
,
DEOXYRIBONUCLEIC ACID
  (
DNA
),
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 C
1
 transfers. Tetrahydrofolate
(also known as FH
4
) serves as an intermedi-
ate carrier (molecule) of methyl, hydroxy-
methyl, 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 metab-
olite 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 thermo-
philes generally found near geothermal vents
beneath bodies of water. See also 
THERMO-
PHILE
,
THERMODURIC
,
EXTREMOPHILIC BACTERIA
,
MESOPHILE
,
PSYCHROPHILE
.
Thioesterase A “family” of enzymes naturally
produced within some plants, such as the Cal-
ifornia bay tree (Umbellularia californica).
Thioesterase catalyzes those plants’ produc-
tion 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
,
THROMBOMODU-
LIN
,
THROMBOLYTIC AGENTS
,
FIBRIN
,
FIBRINOLYTIC
AGENTS
,
CASCADE
.
© 2002 by CRC Press LLC

T
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
 (
t
PA
).
Thrombomodulin A cell surface protein
found on endothelial cells that plays a key
role in modulating the final step in the coag-
ulation process. After thrombin binds to
thrombomodulin, thrombin loses its ability
to cleave fibrinogen to form fibrin. In addi-
tion, 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, throm-
bomodulin modulates the activity of the
enzyme thrombin causing a cessation of full-
blown clotting activity. See also 
THROMBIN
,
PROTEIN
,
PROTEIN C
,
THROMBOSIS
,
PATHWAY
,
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
 (
t
PA
).
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
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

T
dish environment which contains the nutri-
ents necessary for cell growth. One use of
tissue culture is to produce disease free off-
spring from certain (valuable, high quality)
crop plants. Another use of tissue culture
methods is for “embryo rescue” to enable
“wide crosses” between two different spe-
cies of plants. In that procedure, pollen from
one plant species (e.g., a wild plant possess-
ing disease resistance) is induced to fertilize
a plant from another species (e.g., a domes-
ticated crop). The resultant fertilized plant
embryo, which would not grow on its own,
is “rescued” via tissue culture methods. Fol-
lowing maturation, that wide cross (i.e., a
hybrid plant from two species that normally
would not cross) produces fertile seeds on
its own without any need for further inter-
vention by man. See also 
CELL
,
ORGANISM
,
CULTURE MEDIUM
,
SPECIES
,
HYBRIDIZATION
(
PLANT GENETICS
).
Tissue Plasminogen Activator (tPA) A glyco-
protein that possesses thrombolytic (i.e.,
blood clot-dissolving) activity. It is used as
a drug to dissolve clots and acts by first
binding to fibrin (clots). It then activates
(i.e., proteolytically cleaves) plasminogen
(molecules) to yield plasmin, a bloodborne
enzyme that itself cleaves molecular bonds
in the fibrin clot. The plasmin molecules dif-
fuse through the fibrin clot and cause the clot
to dissolve rapidly. With the dissolution of
the clot, blood flow to the formerly blocked
blood vessel (e.g., the heart) is restored. See
also
THROMBUS
,
THROMBIN
,
THROMBOLYTIC
AGENTS
,
GLYCOPROTEIN
,
FIBRIN
,
FIBRINOLYTIC
AGENTS
.
TKI See
TYROSINE KINASE INHIBITORS
.
TME (N) Abbreviation for “true metaboliz-
able energy (corrected for nitrogen)”; a mea-
sure of the amount of energy that a given
animal (e.g., chicken) can extract from a
given feed ration. See also 
METABOLISM
,
CHEMOMETRICS
,
CALORIE
.