though slightly different in structure (e.g., via site-directed mutagenesis) in an attempt to create a molecule that is a “perfect fit” (e.g., to receptor). See also RATIONAL DRUG

DESIGN, DEOXYRIBONUCLEIC ACID (DNA), RIBO-

NUCLEIC ACID (RNA), RECEPTORS, RECEPTOR FIT-

TING (RF), RECEPTOR MAPPING (RM), MOIETY,

POLYMERASE CHAIN REACTION (PCR), SITE-

DIRECTED MUTAGENESIS, DIVERSITY BIOTECHNOL-

OGY CONSORTIUM, COMBINATORIAL CHEMISTRY,

COMBINATORIAL BIOLOGY.

Molecular Evolution S e e C O M B I N A T O R I A L

CHEMISTRY.

Molecular Fingerprinting See C O M B I N A T O -

RIAL CHEMISTRY.

Molecular Genetics The science dealing with the study of the nature and biochemistry of the genetic material. Includes the technolo-

Monoclonal Antibodies (MAb) Discovered and developed in the 1970s by Cesar Milstein and Georges Kohler, monoclonal antibodies are the name for antibodies derived from a single source or clone of cells that recognize only one kind of antigen. Made by fusing myeloma cancer cells (which multiply very fast) with antibody-producing cells, then spreading the resulting conjugate colony so thin that each cell can be grown into a whole, separate colony (i.e., cloning). In this way, one gets whole batches of the same (monoclonal) antibody, which are all specific to the same antigen.

Monoclonal antibodies have found markets in diagnostic kits and show potential for use in drugs (e.g., to shrink tumors), imaging agents, and in purification processes. One example of a diagnostic use is the invention in 1997 by Bruno Oesch of a monoclonal antibody-based rapid test to detect the prion (PrP 5c) that causes bovine spongiform encephalopathy (BSE) in cattle. See also

ASCITES, MYELOMA, TUMOR, CORN, IMMUNO-

TOXIN, BLAST CELL, ANTIGEN, ANTIBODY, SINGLE-

DOMAIN ANTIBODIES (dAbs), MURINE, CATALYTIC

ANTIBODY, SEMISYNTHETIC CATALYTIC ANTIBODY,

BSE, PRION, HER-2 GENE.

Monocytes Also called monocyte macrophages. The round-nucleated cells that circulate in the blood. In summary they engulf and kill microorganisms, present antigen to the lymphocytes, kill certain tumor cells, and are involved in the regulation of inflammation.

These cells are often the first to encounter a foreign substance or pathogen or normal cell debris in the body. When they do, the material is taken up (engulfed) and degraded by means of oxidative and hydrolytic enzymatic attack. Peptides that result from the degradation of foreign protein are then bound to a monocyte protein called class II MHC (major histocompatibility complex) and this self-foreign complex then migrates to the surface of the cell where it is embedded into the cell membrane in such a way as to present the peptide to the outside of the cell. This positioning allows T lymphocytes to recognize (inspect) the peptide. Whereas self-peptides derived from normal cellular debris are ignored, foreign peptides activate

precursors of helper T cells to further mature into active, lymphokine-secreting helper T lymphocytes, also known as TH cells. When monocytes move out of the bloodstream and into the tissues they are then called macrophages. See also MACROPHAGE,

CELLULAR IMMUNE RESPONSE, PATHOGEN, MHC.

Monoecious A category of plants (e.g., the soybean plant) that possess both male and female reproductive structures on the same plant. Thus, such plants are capable of selfpollination. For example, 95% of the pollen from a soybean plant (Glycine max) does not leave the flower in which it was produced. Virtually none of a given soybean plant’s pollen leaves the plant in which it was produced.

See also SOYBEAN PLANT, BARNASE.

Monomer The basic molecular subunit from which, by repetition of a single reaction, polymers are made. For example, amino acids (monomers) link together via condensation reactions to yield polypeptides or proteins (polymers). A monomer is analogous to a link (monomer) in a metal chain (polymer). See also POLYMER.

Monosaccharides The chemical building blocks of carbohydrates, hence known as “simple sugars.” They are classified by the number of carbon atoms in the (monosaccharide) molecule. For example, pentoses have five and hexoses have six carbon atoms. They normally form ring structures. The empirical formula for monosaccharides is

(CH2O)n. See also OLIGOSACCHARIDES, CARBOHYDRATES, SUGAR MOLECULES.

Monounsaturated Fats Fat molecules possessing one less than the maximum possible number of hydrogen atoms (on that given fat molecule). Diets that are high in monounsaturated fat content have been shown to reduce low-density lipoproteins (“bad” cholesterol) blood content, while leaving blood levels of high-density lipoproteins (“good” cholesterol) essentially unchanged. See also FATTY

ACID, SATURATED FATTY ACIDS, DEHYDROGENA-

TION, UNSATURATED FATTY ACID, LOW-DENSITY

LIPOPROTEINS (LDLP), HIGH-DENSITY LIPOPRO-

TEINS (HDLPs), OLEIC ACID, FATS.

Monounsaturated Fatty Acids (MUFA)

Refers to the category of those fatty acids (e.g., oleic acid) that possess one less than

the maximum possible number of hydrogen atoms (e.g., possible to be attached to the molecular structure of oleic acid). Enzymes (e.g., ∆12 desaturase) present in some oilseed plants (soybean, corn/maize, canola, etc.) convert some MUFAs to polyunsaturated fatty acids (PUFAs) within their developing seeds. Diets that are high in monounsaturated fatty acid content have been shown to reduce low-density lipoproteins (“bad” cholesterol) blood content while simultaneously leaving blood levels of highdensity lipoproteins (“good” cholesterol) essentially unchanged. Soybean oil has historically averaged approximately 24.5% monounsaurated fatty acid content by

weight. See also MONOUNSATURATED FATS,

FATTY ACID, UNSATURATED FATTY ACID, SOYBEAN

OIL, OLEIC ACID, LOW-DENSITY LIPOPROTEINS

(LDLP), DELTA 12 DESATURASE, POLYUNSATU-

RATED FATTY ACIDS (PUFA).

Multi-Copy Plasmids P l a s m i d s p r e s e n t inside bacteria in quantities greater than one plasmid per (host) cell. See also PLASMID,

VECTOR, COPY NUMBER.

Multienzyme System A sequence of related enzymes participating in a given metabolic (chemical reaction) pathway.

Multiple Sclerosis A disease in which the human body’s immune cells attack myelin (the “insulation” that surrounds nerve fibers in the spinal cord and brain) and the body’s acetyl choline receptors. That leads to recurrent muscle weakness, loss of muscle control, and (potentially) eventual paralysis. See

also AUTOIMMUNE DISEASE, THYMUS, ACETYLCHOLINE, RECEPTORS, IMMUNE RESPONSE, NEUROTRANSMITTER, EXCITATORY AMINO ACIDS

(EAAs).

Multipotent Adult Stem Cell Certain stem cells present within (adult) bodies of organisms, that can be differentiated (via chemical signals) to give rise to a variety of different cell/tissue types (bone, cartilage, fat, muscle, red blood cells, B cells, T cells, etc.). See

Malso STEM CELLS, CELL, ORGANISM, SIGNALING,

RED BLOOD CELLS, B CELLS, T CELLS, MESODER-

MAL ADULT STEM CELLS.

Murine Of, or pertaining to, mice. For example, the first monoclonal antibodies were produced using cells from mice. This frequently caused adverse immune responses to monoclonal antibodies when they were injected into the human body (e.g., thus limiting their use in therapeutic purposes). However, researchers have recently discovered how to make monoclonal antibodies in

human cells. See also MONOCLONAL ANTIBODIES

(MAb).

Muscular Dystrophy (MD) A genetic disease caused by a defect in the X chromosome (resulting in nonexpression of the Duchenne Muscular Dystrophy gene); first recognized by G. A. B. Duchenne in 1858. The disease afflicts males almost exclusively because males have only one X chromosome, whereas females inherit two copies of the X chromosome and have a “backup” in case one X chromosome is damaged (as is the case for MD victims). In 1981, Kay E. Davies used DNA probes (genetic probes) to discover that the Duchenne Muscular

Dystrophy (DMD) gene must lie somewhere between two unique (to MD victims) segments on the upper, shorter arm of the X chromosome. See also DNA PROBE, CHRO-

MOSOMES, KARYOTYPE, CHROMATIDS, CHROMA-

TIN, SINGLE-NUCLEOTIDE POLYMORPHISMS (SNPs).

Mutagen A chemical substance capable of producing a genetic mutation (change), by causing changes in the DNA of living organisms. For example, Dr. Gary Shaw discovered in 1996 that women who smoke cigarettes during their pregnancies are twice as likely to have babies with the genetic deformity known as cleft lip and palate. If those women have a particularly susceptible (to smoke) gene variant (allele) within their DNA, they are as much as eight times as likely to have babies with cleft lip and palate. According to the World Health Organization (WHO), 60–80% of all known mutagens are also carcinogens (cancer-causing). See also

MUTATION, GENE, GENETICS, HEREDITY, GENETIC CODE, CANCER, CARCINOGEN, ALLELE, DEOXY-

RIBONUCLEIC ACID (DNA), ONCOGENES, MUTANT,

ANTIOXIDANTS.

Mutant An altered cell or organism resulting from mutation (an alteration) of the original wild (normal) type. A change from the normal to the unique or abnormal. See also

MUTAGEN, HEREDITY, WILD TYPE.

Mutase An enzyme catalyzing transposition of a functional group in the substrate (substance acted upon by the enzyme). Intramolecular transfer of a chemical group from one position (i.e., carbon atom) to another within the same molecule. An example of a mutase is phosphoglucomutase. It has a molecular weight of about 60,000 Daltons with about 600 amino acid residues (monomers). The mutase can interchange (move) a phosphate unit between the 1 and 6 position. The 1 refers to a carbon atom designated as “#1” and the 6 refers to a different carbon atom designated as “#6.”

Mutation From the Latin term mutare, meaning to change. Any change that alters the sequence of the nucleotide bases in the genetic material (DNA) of an organism or cell; with alteration occurring either by displacement, addition, deletion, cross-linking, or other destruction. The mutation alteration

to the DNA sequence would alter its meaning, i.e., its ability to produce the normal amount or normal kind of protein, so the organism or cell is itself altered. Such an altered organism is called a mutant. See also

MUTANT, INFORMATIONAL MOLECULES, HERED-

ITY, GENETIC CODE, GENETIC MAP, PROTEIN,

DEOXYRIBONUCLEIC ACID (DNA).

Mutation Breeding Refers to several techniques, involving induced mutations, that were utilized by some crop plant breeders (primarily in the 1960s and 1970s) to introduce desirable genes into the plants with which they were working. For example, gene(s) to confer resistance to plant diseases, increased yield per acre/hectare or improvements in composition that were not present within the historic/natural germplasm of that plant species. These new-to-that-species genes were “created” via soaking its seeds or pollen in mutation-causing chemicals (i.e., mutagens), or via bombardment of seeds with ionizing radiation; followed by grow-out of the resultant plants and selection of the particular mutation (i.e., beneficial trait) desired by the plant breeder. That plant was then propagated via straightforward breeding to yield seeds that are still sown

today. See also TRADITIONAL BREEDING METHODS, MUTATION, MUTAGEN, GENE, TRAIT, WHEAT,

BARLEY, POINT MUTATION.

Mutual Recognition Agreements (MRAs)

Legal agreements (treaties) between two or more nations, to recognize and respect each other’s approval process (e.g., for new crops derived via biotechnology). See also GMO,

COMMITTEE FOR VETERINARY MEDICINAL PRODUCTS (CVMP), ORGANIZATION FOR ECONOMIC COOPERATION AND DEVELOPMENT

EVENT, EUROPEAN MEDICINES EVALUATION AGENCY (EMEA), COMMITTEE FOR PROPRIETARY MEDICINAL PRODUCTS (CPMP), UNION FOR PROTECTION OF NEW VARIETIES OF PLANTS (UPOV).

Mutual Recognition Arrangements S e e

MUTUAL RECOGNITION AGREEMENTS (MRAs).

Mycobacterium tuberculosis The pathogen that causes tuberculosis, a human disease in which the lungs are destroyed as this bacteria grows (within lung tissue). In 1998, scientists completed sequencing of the genome of

Mycobacterium tuberculosis. Recently, a new strain of M. tuberculosis, that is resistant to virtually all commercial antibiotics, has begun to infect some people. See also

BACTERIA, PATHOGEN, SEQUENCING (OF DNA

MOLECULES), ANTIBIOTIC, ANTIBIOTIC RESISTANCE,

GENOME, STRAIN.

Mycotoxins Toxins produced by fungi. More than 350 different mycotoxins are known to man, but the first ones to be isolated and scientifically characterized (i.e., described) were the aflatoxins, in 1961. The second group of mycotoxins to be isolated and characterized were the ochratoxins, in 1965.

Almost all mycotoxins possess the capacity to harmfully alter the immune systems of animals. Consumption by animals (includ-

ing humans) of certain mycotoxins (via eat- M ing infected corn/maize, wheat, certain tree

nuts, peanuts, cottonseed products, etc.) can result in liver toxicity, gastrointestinal lesions, cancer, muscle necrosis, etc. See

also TOXIN, FUNGUS, FUSARIUM, AFLATOXIN,

VOMITOXIN, FUSARIUM MONILIFORME, FUMONISINS,

ZEARALENONE, OCHRATOXINS, ERGOTAMINE.

Myeloma A tumor cell line derived from a lymphocyte. It usually produces a single type of immunoglobulin. See also

DOMA, LYMPHOCYTE, AGING.

Myoelectric Signals The nerve signals that are sent by the body in order to control muscle movement.

Myristoylation Transformation of proteins in cells in such a manner that these cells then cause cancer. See also CANCER.