Biotechnology

TMEn See
TME
 (
N
).
Tobacco Budworm See
HELIOTHIS VIRESCENS
(
H
.
VIRESCENS
).
Tobacco Hornworm Caterpillars (pupae) of
the Lepidopteran insect Manduca sexta.
Tobacco Hornworm is susceptible to
Cry1A(b) protein (e.g., they are killed if they
eat plants genetically engineered to contain
Cry1A(b) protein). See also 
CRY
1
A
(b)
PROTEIN
.
Tobacco Mosaic Virus (TMV) O n e   t h e   o f
smallest viruses, consisting of some 2,200
chains of identical polypeptides and a mol-
ecule of RNA. All of the genetic/heredity
information of the Tobacco Mosaic Virus is
contained in its RNA. The first discovery of
a self-assembling, active biological structure
occurred in 1955, when Heinz Frankel-Con-
rat and Robley Williams showed that TMV
will reassemble into functioning, infectious
virus particles (after the TMV has been dis-
sociated into its components via immersion
in concentrated acetic acid). The TMV virus
infects the leaves of tomato and tobacco
plants, causing disease. Tobacco plants can
be genetically engineered to resist TMV
infection. A tomato plant, genetically engi-
neered to resist TMV infection, has been
commercially available since 1992. See also
GENETIC ENGINEERING
,
CAPSID
,
VIRUS
,
RNA
,
POLYPEPTIDE
  (
PROTEIN
),
GENE
,
INFORMATIONAL
MOLECULES
,
HEREDITY
,
SELF
-
ASSEMBLY
  (
OF A
LARGE MOLECULAR STRUCTURE
).
Tocopherols A “family” of different molecular
forms of vitamin E; each of which has a
saturated phytyl “tail” attached (to the
“backbone” of the molecule). Commercial
tocopherols are extracted from soybeans,
although some are also naturally present in
canola and sunflower. See also 
VITAMIN
,
SOY-
BEAN PLANT
,
VITAMIN E
.
Tocotrienols A “family” of different molecu-
lar forms of vitamin E; each of which has
an unsaturated isoprenoid “side chain”
attached (to the “backbone” of the mole-
cule). Tocotrienols are naturally present in
cereal grains (e.g., oats, barley, rye, and rice
bran). See also 
VITAMIN
,
ISOPRENE
,
VITAMIN E
.
Tomato A green bushy plant, botanical name
Lycopersicon esculentum. The wild type is
native to South America, but the (domesti-
cated) tomato is grown worldwide today. Its
fruit, known as tomatoes, are a natural
source of the antioxidant carotenoid lyco-
pene, a phytochemical whose consumption
has been linked to a reduction in coronary
heart disease and some cancers (e.g., prostate
cancer). See also 
LYCOPENE
,
PHYTOCHEMICALS
,
© 2002 by CRC Press LLC

T
ANTIOXIDANTS
,
CANCER
,
CAROTENOIDS
,
CORONARY
HEART DISEASE
 (
CHD
),
WILD TYPE
.
Tomato Fruitworm See the link. See also
HELICOVERPA ZEA
 (
H
.
ZEA
).
Topotaxis See
TROPISM
.
TOS See
TRANSGALACTO
-
OLIGOSACCHARIDES
.
Totipotency The ability to grow/differentiate
into all of the types of cells/tissues constitut-
ing an (adult) organism’s body. See also 
STEM
CELL ONE
,
CELL
,
ZYGOTE
,
CELL
-
DIFFERENTIATION
,
CELL
-
DIFFERENTIATION PROTEINS
,
TOTIPOTENT
STEM CELLS
.
Totipotent Stem Cells Bone marrow cells that
(when signaled) mature into both red blood
cells and white blood cells. Receptors on the
surface of totipotent stem cells “grasp” pass-
ing blood cell growth factors (e.g., Interleu-
kin-7, Stem Cell Growth Factor, etc.),
bringing them inside these stem cells and
thus causing the maturation and differentia-
tion into red and white blood cells. These
receptors are called FLK-Z receptors. See
also
STEM CELL ONE
,
STEM CELLS
,
WHITE BLOOD
CELLS
,
GROWTH FACTOR
,
RECEPTORS
,
CELL
-
DIF-
FERENTIATION PROTEINS
,
CELL DIFFERENTIATION
,
CELL
.
Toxic Substances Control Act (TSCA) A
1976 American federal law under which the
U.S. Environmental Protection Agency
(EPA) has regulated the release of geneti-
cally engineered organisms (e.g., bacteria or
plants) that produce natural insecticides.
This is based on legal analogy to synthetic
chemical insecticides, which are clearly reg-
ulated under TSCA. See also 
OAB
 (
OFFICE OF
AGRICULTURAL BIOTECHNOLOGY
),
FEDERAL
INSECTICIDE FUNGICIDE AND RODENTICIDE ACT
(
FIFRA
),
GENETICALLY ENGINEERED MICROBIAL
PESTICIDES
  (
GEMP
),
WHEAT TAKE
-
ALL DISEASE
,
BACILLUS THURINGIENSIS
 (
B
.
t
.).
Toxicogenomics A branch of toxicology that
deals with the reactions between toxins and
the specific differences in response of differ-
ent organisms due to their different
genomes/DNA (of the different individuals
that consume the same toxin). For example,
some rare humans can tolerate eating certain
poisonous mushrooms (which sicken or kill
all other humans that consume those partic-
ular mushroom species).
During 2001, Fred Gould, David Heckel,
and Linda Gahan showed that a rare, reces-
sive gene (allele) known as BtR-4 could con-
fer (to tobacco budworms possessing two
copies of that particular gene) resistance to
at least some of the “cry” proteins (which
kill all other tobacco budworms that con-
sume those “cry proteins”). The subgroup of
all those individuals whose DNA (genome)
causes their bodies to resist the effects of a
given toxin, is known as a haplotype. A hap-
lotype could (theoretically) be as small as
one individual, because the particular resis-
tance-to-toxin could result from one single-
nucleotide polymorphism (SNP). See also
GENE
,
GENOMICS
,
PHARMACOGENOMICS
,
TOXIN
,
GENOME
,
DEOXYRIBONUCLEIC ACID
  (
DNA
),
HAP-
LOTYPE
,
SINGLE
-
NUCLEOTIDE POLYMORPHISMS
(
SNP
s
),
RECESSIVE ALLELE
,
CRY PROTEINS
,
TOBACCO BUDWORM
.
Toxigenic E. coli See
E N T E R O H E M O R R H A G I C
E
.
COLI
,
ESCHERICHIA COLIFORM
0157
:
H
7
  (
E
.
COLI
0157
:
H
7
).
Toxin A substance (e.g., produced in some
cases by fungi, weeds, ants, or disease-caus-
ing microorganisms) which is poisonous to
certain other living organisms. See also 
ANTI-
TOXIN
,
ABRIN
,
RICIN
,
COLICINS
,
BACTERIOCINS
,
ESCHERICHIA COLIFORM
0157
:
H
7
 (
E
.
COLI
0157
:
H
7
),
ENTEROHEMORRHAGIC E
.
COLI
,
PFIESTERIA PISCI-
CIDA
,
PHYTOTOXIN
,
PHOTORHABDUS LUMINESCENS
,
ENTEROTOXIN
,
GLUCOSINOLATES
,
ALKALOIDS
,
AFLATOXIN
,
MYCOTOXINS
,
FUNGUS
,.
TPS See
TECHNOLOGY PROTECTION SYSTEM
.
Tracer (radioactive isotopic method) A
metabolite that is labeled by incorporation of
an isotopic atom into its structure. The met-
abolic fate of the labeled metabolite can then
be traced in intact organisms. That is, one is
able to ascertain where (in what kind of struc-
ture) the metabolite ends up as well as the
transformation products (intermediate mole-
cules) that were involved in its formation.
Certain atoms of a given metabolite are
labeled. This is done by substituting radioac-
tive isotopes for the atom in question.
Because an atom is replaced by an isotope,
the metabolite as a whole is chemically and
biologically indistinguishable from its normal
analog. The presence of the isotope allows the
metabolite and its transformation products to
© 2002 by CRC Press LLC

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be detected and measured. Without this tech-
nique, many aspects of metabolism could not
have been studied. These include: the process
of photosynthesis, metabolic turnover rates,
and the biosynthesis of proteins and nucleic
acids. See also 
REASSOCIATION
 (
OF DNA
),
RADIO-
ACTIVE ISOTOPE
,
RADIOIMMUNOASSAY
.
Traditional Breeding Methods A phrase uti-
lized by some people to refer to some or
most techniques/technologies utilzed by
crop plant breeders prior to some arbitrarily
chosen date (after which some people feel
that “genetic engineering” arrived abruptly).
For example, in 1992 Tim Croughan discov-
ered a single rice (Oryza sativa) plant that
had survived (what should have been a lethal
dose of) an imidazolinone-based herbicide,
due to a (mutated) gene in its DNA that made
it resistant to imidazolinones. That plant was
then propagated via straightforward breed-
ing to yield seeds still sown today. Many
years ago, some other crops similarly were
given new traits (e.g., herbicide tolerance,
compositional improvements, etc.) via muta-
tion breeding (i.e., soaking seeds or pollen
in mutation-causing chemicals, or bombard-
ing seeds with ionizing radiation to cause
random genetic mutations, followed by
grow-out and selection of the particular
mutation desired such as herbicide tolerance,
as described above).
Other crops were given new traits via
crossing them with related wild plants,
which occasionally resulted in extremely
high levels of natural toxicants in those
plants/seeds (solanine, psoralene, etc.). Still
others were given new traits via wide-cross-
ing them with other domesticated species
(e.g., the tangelo is a hybrid of the grapefruit
and the tangerine). The U.S. Food and Drug
Administration (FDA) regulates all new crop
plants similarly (e.g., also requires testing of
plants produced via “traditional breeding
methods” for the potential presence of intro-
duced or increased natural toxicants). See
also
GENETIC ENGINEERING
,
HERBICIDE
-
TOLERANT
CROP
,
GENETICS
,
MUTATION
,
MUTATION BREEDING
,
TRAIT
,
CANOLA
,
SOYBEAN PLANT
,
CORN
,
SOLANINE
,
PSORALENE
,
FOOD AND DRUG ADMINISTRATION
(
FDA
),
BARLEY
,
HYBRIDIZATION
 (
PLANT GENETICS
),
MARKER
  (
DNA SEQUENCE
),
MARKER ASSISTED
SELECTION
,
POINT MUTATION
,
SOMACLONAL
VARIATION
,
SOMATIC VARIANTS
,
WIDE CROSS
,
EMBRYO RESCUE
,
TISSUE CULTURE
.
Traditional Breeding Techniques See
TRADI-
TIONAL BREEDING METHODS
.
Trait A characteristic of an organism, which
manifests itself in the phenotype (physi-
cally). Many traits are the result of the
expression of a single gene, but some are
polygenic (result from simultaneous expres-
sion of more than one gene). For example,
the level of protein content in soybeans is
controlled by five genes. See also 
PHENOTYPE
,
GENOTYPE
,
EXPRESS
,
GENE
,
POLYGENIC
,
PROTEIN
,
CALLIPYGE
.
trans Fatty Acids One of the two isomeric
forms that fatty acids can exist in. Trans fatty
acids are naturally present in some meat and
dairy products (which constitute approxi-
mately 5% of the average American diet).
See also 
FATTY ACID
,
ISOMER
,
STEREOISOMERS
,
HYDROGENATION
.
trans-Acting Protein A trans-acting protein
has the exceptional property of acting (having
an effect) only on the molecule of DNA
(deoxyribonucleic acid) from which it was
expressed. See also 
EXPRESS
, cis-
ACTING
PROTEIN
.
Transactivating Protein See
VIRAL TRANSACTI-
VATING PROTEIN
.
Transaminase A large group of enzymes that
catalyze the transfer of the amino group from
any one of at least 12 amino acids to a keto
acid to form another amino acid. Also known
as aminotransferases. See also 
ENZYME
,
AMINO ACID
.
Transamination The reaction of the enzy-
matic removal and transfer of an amino
group from one specific compound to
another. See also 
TRANSAMINASE
,
AMINO ACID
.
Transcript Term used to refer to the various
segment(s) of messenger RNA (mRNA) that
result from transcription of a gene. See also
GENE
,
TRANSCRIPTION
,
MESSENGER RNA
 (
m
RNA
),
TRANSCRIPTOME
,
CENTRAL DOGMA
 (
NEW
).
Transcription The enzyme-catalyzed process
whereby the genetic information contained
in one strand of DNA (deoxyribonucleic
acid) is used as a template to specify and
produce a complementary mRNA strand.
Transcription may be thought of as a rewriting
© 2002 by CRC Press LLC

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of the information contained in DNA into
RNA. The language, however, is the same —
both are nucleic acid-based. This is in con-
trast to translation, in which the information
is translated from one language (RNA,
nucleic acid-based) into another language
(protein, amino acid-based). See also 
GENE
EXPRESSION
,
TRANSLATION
,
MESSENGER RNA
(
m
RNA
),
GENETIC CODE
,
DEOXYRIBONUCLEIC ACID
(
DNA
),
TRANSCRIPTION FACTORS
,
TRANSCRIPTION
UNIT
,
ANTICODING STRAND
.
Transcription Factors Proteins and/or other
chemical compounds that interact with each
other, and with regulatory sequences within
DNA (when immediately adjacent to the
DNA in a cell), to either facilitate (“turn on”)
or inhibit (“turn off “) the activity (i.e., cod-
ing for proteins) of that DNA’s genes. Tran-
scription factors hold potential to:
• Cure diseases (e.g., by blocking the del-
eterious effects of certain disease-caus-
ing genes).
• To assist farmers in crop protection
(e.g., by switching on the genes that
cause crop plants to initiate “cold hard-
ening,” or certain types of insect resis-
tance mechanisms).
• To improve human health (e.g., PUFA
modulation of genes, modulation of
genes by some vitamins, etc.).
Some transcription factors are an integral
component in certain gene expression cas-
cades. For example, a gene expression cas-
cade is initiated by the first gene causing
expression of a transcription factor, which
then itself interacts with the cell’s DNA to
either cause or speed-up yet another gene
expression. The protein resulting from that
second gene expression is yet another tran-
scription factor which triggers another (i.e.,
third) gene expression, and so on. See also
PROTEIN
,
GENETIC CODE
,
CODING SEQUENCE
,
DEOXYRIBONUCLEIC ACID
  (
DNA
),
CELL
,
INHIBI-
TION
,
GENE
,
p53
GENE
,
TRANSCRIPTION
,
p53
PRO-
TEIN
,
CBF
1
,
COLD HARDENING
,
REGULATORY
SEQUENCE
,
EXPRESS
,
GENE EXPRESSION
,
GENE
EXPRESSION CASCADE
,
DOWN REGULATING
,
VITA-
MIN
,
POLYUNSATURATED FATTY ACIDS
  (
PUFA
),
RECOMBINASE
.
Transcription Unit A group of genes that
code for functionally related RNA molecules
or protein molecules. This group of genes is
expressed (transcribed) together (as a unit,
thus the name). See also 
EXPRESS
,
GENE
,
TRAN-
SCRIPTION
,
TRANSLATION
,
GENETIC CODE
,
CODING
SEQUENCE
,
DEOXYRIBONUCLEIC ACID
  (
DNA
),
RIBONUCLEIC ACID
 (
RNA
),
RIBOSOMES
.
Transcriptome Refers to the entire (complete,
possible) set of all gene transcripts (i.e.,
mRNA segments resulting from gene tran-
scription process) in a given organism. Also
to knowledge of their roles in that organ-
ism’s structure, growth, health, disease
(and/or that organism’s resistance to dis-
ease), etc. Those roles are predominantly
due to the impact of each protein molecule
(i.e., resulting from the mRNA segments
being translated in cells’ ribosomes); which
is itself due to the protein molecule’s com-
position and its tertiary conformation (which
determines the protein’s impact in the organ-
ism’s tissues, metabolism, etc.).
More than one protein can result from
each gene in an organism’s genome, due to:
• Interactions between genes.
• Interactions between genes and their
(protein) products.
• Interactions between genes and some
environmental factors.
Mechanistically, this results in different pro-
teins being produced (during translation pro-
cess) via:
• Alternative splicing of the mRNA tran-
script. For example, a single intronic
base substitution that is present within
the IKAP gene (i.e., the allele respon-
sible) for the disease known as familial
dysautonomia affects the splicing of the
IKAP transcript (i.e., the mRNA seg-
ment that determines which specific
protein is subsequently “manufactured”
by the ribosomes).
• Varying translation start or stop site (on
the gene).
• Frameshifting (i.e., different set of trip-
let codons in the mRNA/transcript is
translated by the ribosome).
© 2002 by CRC Press LLC

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See also 
GENE
,
TRANSCRIPT
,
MESSENGER RNA
(
m
RNA
),
CODING SEQUENCE
,
TRANSLATION
,
CODON
,
PROTEIN
,
GENOME
,
GENETIC CODE
,
CENTRAL
DOGMA
  (
NEW
),
ORGANISM
,
CONFORMATION
,
METABOLISM
,
TERTIARY STRUCTURE
,
INTRON
,
BASE
.
Transduction (gene) The transfer of bacterial
genes (DNA) from one bacterium to another
by means of a (temperature or defective)
bacterial virus (bacteriophage). There exist
two kinds of transduction: specialized and
general. In the case of specialized transduc-
tion, a restricted group of host genes becomes
integrated into the virus genome. These
“guest” genes usually replace some of the
virus genes and are subsequently transferred
to a second bacterium. In the case of gener-
alized transduction, host genes become part
of the mature virus particle in place of, or in
addition to, the virus DNA. However, in this
case the genes can come from virtually any
portion of the host genome and this material
does not become directly integrated into the
virus genome. In the case of plants, the vec-
tor can be Agrobacterium tumefaciens. See
also
BACTERIOPHAGE
,
VECTOR
,
GENETIC CODE
,
AGROBACTERIUM TUMEFACIENS
,
RETROVIRAL VEC-
TORS
,
GENE DELIVERY
,
TRANSFECTION
.
Transduction (signal) See
SIGNAL TRANSDUCTION
.
Transfection This term has several different
meanings, depending on the context in
which it is used: A word utilized generally
to refer to insertion of DNA segments
(genes) into cells (via electroporation,
endocytosis, etc.); a special case of transfor-
mation in which an appropriate recipient
strain of bacteria is exposed to (free) DNA
isolated from a transducing phage with the
“take up” of that DNA by some of the bac-
teria and consequent production and release
of complete virus particles. The process
involves the direct transfer of genetic mate-
rial from donor to recipient. See also 
MARKER
(
GENETIC MARKER
),
TRANSFORMATION
,
ELEC-
TROPORATION
,
GENE
,
VIRUS
,
CELL
,
BACTERIA
,
DEOXYRIBONUCLEIC ACID
 (
DNA
),
TRANSDUCTION
(
gene
).
Transfer RNA (tRNA) A class of relatively
small RNA (ribonucleic acid) molecules of
molecular weight 23,000 to about 30,000.
tRNA molecules act as carriers of specific
amino acids during the process of protein
synthesis. Each of the 20 amino acids found
in proteins has at least one specific corre-
sponding tRNA. The tRNA binds covalently
with its specific amino acid and “leads” it to
the ribosome for incorporation into the
growing peptide chain. See also 
RIBONUCLEIC
ACID
  (
RNA
),
MOLECULAR WEIGHT
,
AMINO ACID
,
MESSENGER RNA
 (
m
RNA
).
Transferases Enzymes that catalyze the transfer
of functional groups to molecules (from other
molecules). See also 
TRANSAMINASE
,
ENZYME
,
HEDGEHOG PROTEINS
,
GLYCOSYLTRANSFERASES
.
Transferred DNA See
T
i
PLASMID
.
Transferrin The protein molecule responsible
for transporting iron (molecules) to tissues
throughout the body, via the circulatory sys-
tem. See also 
PROTEIN
,
TRANSFERRIN RECEPTOR
,
HEME
,
BLOOD
-
BRAIN BARRIER
 (
BBB
).
Transferrin Receptor The receptor molecule
(located on the surface of cells throughout
the body) responsible for binding to trans-
ferrin molecules, then bringing those iron-
rich transferrin molecules into the cell where
the iron is released to be used by the cell.
See also 
TRANSFERRIN
,
RECEPTORS
,
HEME
,
BLOOD
-
BRAIN BARRIER
 (
BBB
).