reproduction to growth) also holds true for “seedless” grapes, watermelons, etc. See

also DIPLOID, CHROMOSOMES, WHEAT.

tRNA See TRANSFER RNA (tRNA).

Tropism Orientation movement of a sessile organism in response to a stimulus. Movement of curvature due to an external stimulus that determines the direction of movement. Also known as topotaxis. See also SESSILE,

CHEMOTAXIS.

Trypsin A proteolytic (protein molecular chain-cutting) enzyme produced by the pancreas, to facilitate digestion within certain animals. Trypsin cleaves polypeptide (protein) molecular chains on the carboxyl (group) side of arginine and lysine units (residues); and it is often utilized by man to break apart protein molecules (e.g., to enable scientists to study that protein’s constituent peptides). See also ARGININE (arg), LYSINE (lys),

PROTEIN, PEPTIDE, POLYPEPTIDE (PROTEIN), PRO-

TEOLYTIC ENZYMES, PROTEASES, CHYMOTRYPSIN,

TRYPSIN INHIBITORS, DIGESTION (WITHIN ORGAN-

ISMS), COWPEA TRYPSIN INHIBITOR (CpTI).

Trypsin Inhibitors Compounds present in certain legumes (soybeans, etc.) that inhibit the activity (i.e., protein-cleavage, which aids digestion) of proteases (i.e., proteincleaving enzymes such as trypsin or chymotrypsin) in the digestive systems of monogastric (single-stomach) animals (which include swine, poultry, and humans). Trypsin inhibitors present in traditional varieties of soybeans (botanical name Glycine max (L.) Merrill) include:

• the Kunitz trypsin inhibitor (TI), which T was first isolated and crystallized by M.

Kunitz in 1945. It combines tightly with molecules of trypsin on a 1:1 basis, and thereby reduces the rate of proteincleavage effected by the trypsin enzyme; which inhibits the animal’s digestion of protein(s).

•the Bowman-Birk trypsin inhibitor (BB T.I.), first described by D. E. Bowman in 1944. It combines with molecules of trypsin and chymotripsin, and thereby reduces the rate of protein-cleav- age effected by the trypsin and

chymotrypsin enzymes, which inhibits the animal’s digestion of protein(s).

NOTE: During 2000, research by Frank Meyskins and William Armstrong indicated that consumption of BB T.I. in a manner that ‘bathes’ mouth tissues in it (for extended period of time) inhibits the development of the precancerous mouth lesions that can become oral cancer.

•certain free fatty acids and their acyl CoA esters, which reduce the rate of protein-cleavage effected by the trypsin enzyme inhibiting the animal’s digestion of protein(s).

Heating of soybeans to a temperature of 212° (100°C) for 15 min causes these trypsin inhibitors to be rendered inactive in soybeans, so the animal’s digestion is unimpeded when it is fed soy that has been thus

heated. See also TRYPSIN, CHYMOTRYPSIN, SOYBEAN PLANT, PROTEIN, PROTEASES, ENZYME, PRO-

T E O L Y T I C E N Z Y M E S , D I G E S T I O N (W I T H I N

ORGANISMS), POLYPEPTIDE (PROTEIN), BIOLOGICAL

ACTIVITY, ACYL CoA, COWPEA TRYPSIN INHIBITOR

(CpTI), ORAL CANCER.

Tryptophan (trp) An essential amino acid, it is a precursor of the important biochemical molecules indoleacetic acid, serotonin, and nicotinic acid. L-Tryptophan is used as a common feed additive for livestock to ensure that their diet includes an adequate amount of this essential amino acid. See also ESSEN-

TIAL AMINO ACIDS, STEREOISOMERS, SEROTONIN,

AMINO ACID.

TSH See THYROID STIMULATING HORMONE (TSH).

Tuberculosis See MYCOBACTERIUM TUBERCULOSIS.

Tubulin A cell protein required for cell mitosis (i.e., the cell-reproduction process in which a cell divides into two identical cells). When the drugs paclitaxel or Taxol™ are administered to the body (e.g., in chemotherapy), they bind tubulin; which halts cell division and causes apoptosis in the affected cells (e.g., tumor cells) by binding Bc1-2 (a protein that prevents apoptosis in cells). See also

CELL, PROTEIN, MITOSIS, PACLITAXEL, TAXOL, CANCER, CHEMOTHERAPY, APOPTOSIS.

Tumor A mass of abnormal tissue that resembles normal tissues in structure, but which

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fulfills no useful function (to the organism) and grows at the expense of the body. Tumors may be malignant or benign. Malignant tumors (which infiltrate adjacent healthy tissues) can result from oncogenes and/or carcinogens. They can eventually kill their host if unchecked. Epidermal growth factor encourages rapid cell growth in more than 50% of human tumors. See also CANCER,

ANGIOGENESIS, ONCOGENES, PROTO-ONCOGENES,

CELL, CARCINOGEN, TYROSINE KINASE, TYROSINE

KINASE INHIBITORS (TKI), ATP SYNTHASE, EPIDER-

MAL GROWTH FACTOR (EGF).

Tumor Necrosis Factor (TNF) Literally, tumor death factor. A cytokine (protein that helps regulate the immune system) that has shown potential to combat (kill) malignant (cancer) tumors. Tumor necrosis factor was discovered to be 10,000 times more toxic in humans than in rodents, where it had been tested for toxicity prior to human clinical tests. This example illustrates one potential pitfall of nontarget animal testing in that sometimes animal testing does not accurately reflect or foretell what will happen in humans. Another drawback to using TNF as a drug to combat human tumors is the fact that it is one of the substances released (in the disease rheumatoid arthritis) that destroys tissue in the joints. When released as part of the AIDS (disease), TNF causes cachexia, which is a “wasting away” of the body due to the body’s inability to process nutrients received via digestion. See also

CYTOKINES, LYMPHOKINES, NECROSIS, TUMOR,

TUMOR-INFILTRATING LYMPHOCYTES (TIL CELLS),

PROTEIN, AUTOIMMUNE DISEASE, T CELL MODU-

LATING PEPTIDE (TCMP), DIGESTION (WITHIN

ORGANISMS).

Tumor-Associated Antigens Discovered by Thierry Boon in 1991, these are distinctive protein molecules that are produced in the surface membrane of tumor cells. These protein molecules are used by the body’s cytotoxic T cells to recognize (and destroy) tumor cells, so such proteins hold promise for use in vaccines. See also MAJOR HISTO-

COMPATIBILITY COMPLEX (MHC), MACROPHAGE,

TUMOR, T CELL RECEPTORS, ANTIGEN, T CELLS,

PROTEIN, CELL, CYTOTOXIC T CELLS, HUMAN

LEUKOCYTE ANTIGENS (HLA).

Tumor-Infiltrating Lymphocytes (TIL cells)
The white blood cells of a cancer patient
which have been:
1. Taken from that patient’s tumor (where
those white blood cells had been
attempting to combat the cancer, albeit
unsuccessfully).
2. Stimulated with doses of interleukin-2
(to make the lymphocytes more effec-
tive against the cancer).
3. Multiplied in vitro (i.e., outside of the
patient’s body) to make them more
numerous (and thus more likely to suc-
cessfully combat the cancer).
When these “souped up” lymphocytes
(white blood cells) are reintroduced into that
same patient’s body, the lymphocytes (now
called TIL cells because they have been
“souped up”) attack the cancer tumor
(malignant growth) more vigorously than
before. See also TUMOR, WHITE BLOOD CELLS,
LYMPHOCYTE, LYMPHOKINES, T CELLS, CYTOTOXIC
T CELLS.
Tumor-Suppressor Genes Also called anti-
cancer genes. Genes within a cell’s DNA that
code for (cause to be manufactured in cell’s
ribosomes) proteins that hold the cell’s
growth in check. If these genes are damaged
(e.g., by radiation, by a carcinogen, or by
chance accident in normal cell division),
they no longer hold cell growth in check —
and the cell becomes malignant (if the cell’s
DNA also contains a gene called an onco-
gene). Oncogenes must be present for the
cell to become malignant, but oncogenes
cannot cause a cell to become malignant	T
until a tumor-suppressor gene is damaged.
As with all genes, tumor-suppressor genes
are inherited in two copies (alleles, one from
each parent) and either copy can code for
the proteins necessary for cell growth con-
trol. However, an organism born with one
defective copy of a tumor-suppressor gene
(or in whom one copy is damaged early in
life) is especially prone to cancer (malig-
nancy). See also GENE, p53 GENE, GENETIC
CODE, MEIOSIS, DEOXYRIBONUCLEIC ACID (DNA),
CARCINOGEN, RIBOSOMES, ONCOGENES, CANCER,
TUMOR, PROTO-ONCOGENES, PROTEIN.

© 2002 by CRC Press LLC

Tumor-Suppressor Proteins Proteins that are coded for (caused to be manufactured in the cell’s ribosomes) by tumor-suppressor genes (e.g., the p53 gene). Such proteins (e.g., the p53 protein) then act upon the cell’s DNA in order to prevent uncontrolled cell growth and division (i.e., cancer). See also TUMOR-

SUPPRESSOR GENES, GENE, p53 GENE, PROTEIN,

GENETIC CODE, MEIOSIS, DEOXYRIBONUCLEIC

ACID (DNA), RIBOSOMES, ONCOGENES, CANCER,

TUMOR, CELL, PROTO-ONCOGENES.

Turnover Number The number of molecules of a product produced per minute by a sin- gle-enzyme molecule when that enzyme is working at its maximum rate. That is, the number of substrate molecules converted into a product by one enzyme molecule per minute when that enzyme is “going (catalyzing) as fast as it can.” See also ENZYME,

TRANSFERASES, PROTEASE, PROTEIN KINASES,

PROTEOLYTIC ENZYMES, TRANSAMINASE.

Two-Dimensional (2D) Gel Electrophoresis

A technology/methodology developed during the 1970s to separate the various proteins within a given biological sample, prior to their analysis. The proteins are moved by applying an electrical field. The sample is moved through two different gels (i.e., two different dimensions). The initial gel has a pH gradient that separates the different proteins based on their respective isoelectric points. The second gel (dimension) the sample is moved through is a gel that separates the protein molecules based on their individual molecular weights. That gel acts as a “molecular sieve” (i.e., smaller proteins move faster — and farther — than larger proteins do through this gel; in a fixed

Tamount of time).

A fixed-time gel run (i.e., with appropriate gel and the appropriate electrical field applied to the gel) leaves a scientist with approximately 1,000 “spots” (of protein molecules) on the gel. Each “spot” is a collection of the molecules of one protein (or of several proteins with similar molecular weights) from the original sample (mixture). To identify the protein(s) in the “spots,” the scientist stains them, then assesses the entire gel with an electronic image scanner (or he assesses it visually). From the pattern (coupled

with intensity) of the “spots,” two such gels could be utilized to confirm if two organisms were the same species/strain/variety, or to determine the differences (in gene expression) between samples of diseased vs. healthy tissues. See also PROTEIN, GEL, ELEC-

TROPHORESIS, AGAROSE, POLYACRYLAMIDE GEL

ELECTROPHORESIS (PAGE), PAGE, ISOELECTRIC

POINT, GENE EXPRESSION ANALYSIS, PROTEOMICS,

MOLECULAR WEIGHT, SPECIES.

Type I Diabetes The form of diabetes disease that usually strikes young people (thus, it was formerly known as juvenile or insulindependent diabetes). This disease is characterized by the body’s immune system destroying the insulin-producing cells (Beta cells) of the pancreas. If not treated in time (i.e., via insulin injections), the person can die suddenly. Even when treated, the person is at increased risk of blindness, atherosclerosis, coronary heart disease, heart attack, stroke, and kidney disease. See also DIABETES,

BETA CELLS, PANCREAS, INSULIN, INSULIN-DEPEN-

DENT DIABETES MELLITIS (IDDM), CALPAIN- 10,

ATHEROSCLEROSIS, CORONARY HEART DISEASE

(CHD), TYPE II DIABETES.

Type II Diabetes The form of diabetes disease that usually strikes people who are more than 40 years old. Also known as adult-onset diabetes, this disease is characterized by the body’s tissues becoming insensitive to insulin. Effects on the body include increased likelihood of blindness, atherosclerosis, coronary heart disease, heart attack, stroke, and kidney disease. See also DIABETES, INSULIN-

DEPENDENT DIABETES MELLITIS (IDDM), INSULIN,

CALPAIN- 10, ATHEROSCLEROSIS, CORONARY HEART

DISEASE (CHD), TYPE I DIABETES, INOSITOL.

Type Specimen The actual physical specimen (e.g., a stuffed lizard or a dried insect) that a scientist (who describes and names a previously unknown species) must place in a museum (or other recognized repository) in order to have the right to name that newly discovered species. This “officially deposited specimen” is required for three purposes:

1.So that comparisons can later be made if there is ever a doubt whether another “new” species is simply a member of

© 2002 by CRC Press LLC

this same species (and thus already named)

2.So that taxonomists (who determine and keep the official scientific names by which scientists must refer to each of the world’s organisms) can name each of the newly discovered species in accordance with the complex rules of the International Codes for Nomenclature. Examples of such names in this glossary are Arabidopsis thaliana, Escherichia coli, and Agrobacterium tumefaciens.

3.So that patent claims for genetically engineered organisms can later be enforced.

See also SPECIES, STRAIN, CLADISTICS, CHAKRA-

BARTY DECISION, AMERICAN TYPE CULTURE COL-

LECTION (ATCC), CONSULTATIVE GROUP ON

INTERNATIONAL AGRICULTURAL RESEARCH

(CGIAR).

Tyrosine (tyr) A phenolic α-amino acid. It is a precursor of the hormones epinephrine, norepinephrine, thyroxine, and triiodothyronine. It is also a precursor of the molecule known as melanin (which is the pigment of a suntan). See also AMINO ACID, HORMONE.

Tyrosine Kinase Inhibitors (TKI) Refers to various chemical compounds that inhibit the activity of tyrosine kinase enzyme (inside the body). One example of TKI is genistein. Because the activity of tyrosine kinase helps cancerous (tumor) cells to metastasize (spread/grow), consumption by humans of relevant TKI acts to help prevent (spreading of) certain cancers. See also ENZYME,

TYROSINE KINASE, PROTEIN TYROSINE KINASE

INHIBITOR, BIOLOGICAL ACTIVITY, CANCER, CELL,

TUMOR, GENISTEIN, ISOFLAVONES.

T

© 2002 by CRC Press LLC