as benzene, hexane, isooctane, and oils such as corn and sesame. The structure of an RM is the reverse of that of a micelle. Reverse micelles may be characterized by a structure in which the polar groups of the surfactant and any water present are centrally located with the surfactant hydrocarbon chains pointing outward into the surrounding hydrocarbon medium. Reverse micelles may be used to solubilize polar molecules (i.e., water, enzymes) in organic nonpolar solvents and oils. See also AMPHIPATHIC MOLE-

CULES, MICELLE, SURFACTANT.

Reverse Phase Chromatography (RPC) A method of separating a mixture of proteins or nucleic acids or other molecules by specific interactions of the molecules with a hydrophobic (“water hating”) immobilized phase (i.e., stationary substrate) which interacts with hydrophobic regions of the protein (or nucleic acid) molecules to achieve (preferential) separation of the mixture. See also

CHROMATOGRAPHY.

Reverse Transcriptases Also known as RNAdirected DNA polymerases. A class of enzymes first discovered to be present in RNA tumor-virus, which allows the synthesis of DNA (complementary to the RNA) using the RNA present in the virus as a template. This is the reverse of what normally happens and hence the name. Reverse transcriptases closely resemble the DNAdirected DNA polymerases in that they require the same materials and conditions as

Rthe DNA polymerases (e.g., for RT-PCR).

See also ENZYME, VIRUS, RIBONUCLEIC ACID

(RNA), CENTRAL DOGMA (NEW), POLYMERASE,

RT-PCR.

Reversed Micelle See REVERSE MICELLE (RM).

RFLP (restriction fragment length polymorphism) Restriction fragment length polymor-

phism. See also POLYMORPHISM (CHEMICAL),

RESTRICTION ENDONUCLEASES, RESTRICTION FRAG-

MENT LENGTH POLYMORPHISM (RFLP) TECHNIQUE.

rh Used to denote compounds (human molecules) made through the use of recombinant DNA technology. Recombinant (r) human

(h). See also rhTNF, RECOMBINANT DNA (rDNA),

RECOMBINATION, GENETIC ENGINEERING.

Rhizobium (bacteria) Refers to several strains of bacteria that live in the soil and colonize

the roots of certain plants (i.e., legumes) symbiotically to thereby “fix” nitrogen from the air (i.e., change gaseous nitrogen into the chemical form that can be used by plants). For the legume known as the soybean plant (Glycine max L.), the relevant strain of the bacteria is Rhizobium japonicum. For the legume known as the alfalfa plant, the relevant strain of the bacteria is Sinorhizobium

meliloti. See also BACTERIA, NITROGEN F I X A T O N , N O D U L A T I O N , S O Y B E A N P L A N T ,

SYMBIOTIC, PHARMACOENVIROGENETICS.

Rhizoremediation See

RHIZOBIUM (BACTERIA).

Rho Factor A protein involved in (chemically) assisting Escherichia coli RNA polymerase in the termination of transcription at certain (rho-dependent) sites on the DNA

molecule. See also TRANSCRIPTION, POLYMERASE, ESCHERICHIA COLIFORM (E. COLI).

rhTNF Recombinant human TNF. See also

TUMOR NECROSIS FACTOR (TNF).

RIA See RADIOIMMUNOASSAY.

Ribonucleic Acid (RNA) A long-chain, usually single-stranded nucleic acid consisting of repeating nucleotide units containing four kinds of heterocyclic, organic bases: adenine, cytosine, guanine, and uracil. These bases are conjugated to the pentose sugar ribose and held in sequence by phosphodiester (chemical) bonds.

The primary function of RNA is protein synthesis within a cell. However, RNA is involved in various ways in the processes of expression and repression of hereditary information. The three main functionally distinct varieties of RNA molecules are:

(1) messenger RNA (mRNA), which is involved in the transmission of DNA information, (2) ribosomal RNA (rRNA), which makes up the physical machinery of the synthetic process, and (3) transfer RNA (tRNA), which also constitutes another functional part of the machinery of protein synthesis.

See also HEREDITY, GENETIC CODE, RIBOSOMES,

INFORMATIONAL MOLECULES, NANOTECHNOLOGY.

Ribose D-Ribose, a five-carbon-atom monosaccharide (i.e., a sugar). It is important to life because it and the closely allied compound deoxyribose form a part of the molecules

that constitute the backbone of nucleic acids.

See also NUCLEIC ACIDS, MONOSACCHARIDES.

Ribosomal RNA See rRNA (RIBOSOMAL RNA).

Ribosomes The molecular “machines” within cells that coordinate the interplay of tRNAs, mRNAs, and proteins in the complex process of protein synthesis (manufacture). RNA constitutes nearly two-thirds of the mass of these large (mega-Dalton) molecular assemblies, which are technically ribozymes (i.e., an enzyme in which the catalysis is performed by RNA).

The formation of a ribosome (in the endoplasmic reticulum of a cell) from individual RNA and protein molecules is largely a selfassembly process, because all of the information needed for the correct assembly of this structure is contained in the primary structure of its (molecular) components. The assembly process is ordered and proceeds in stages. Many ribosomes (in a given cell) can simultaneously translate an mRNA molecule. The structure, consisting of a group of ribosomes bound to an mRNA molecule actively synthesizing protein, is called a polyribosome or a polysome. The ribosomes in this (polysome) unit operate independently of each other, each synthesizing a complete polypeptide (protein) “molecular chain.” See

also PROTEIN, POLYPEPTIDE (PROTEIN), PROTEIN

SIGNALING, PROTEIN FOLDING, POLYCISTRONIC,

PROTEIN STRUCTURE, PRIMARY STRUCTURE, TRAN-

SCRIPTION, TRANSCRIPTION UNIT, MESSENGER RNA

(mRNA), CELL, ENDOPLASMIC RETICULUM (ER),

TRANSFER RNA (tRNA), rRNA (RIBOSOMAL rRNA),

DALTON, SELF-ASSEMBLY (OF A LARGE MOLECU-

LAR STRUCTURE), RIBOZYMES, RIBONUCLEIC ACID

(RNA).

Ribozymes Discovered by Thomas Cech and Sidney Altman, they are RNA molecules that act as enzymes; that is, possess catalytic activity and can specifically cleave (cut) other RNA molecules. The ribozyme (RNA) molecule and the other RNA molecule come together, whereupon the ribozyme molecule cuts the other RNA molecule at a specific defined (three-base) site. Because the ribozyme molecule acts as an enzyme in this reaction, the ribozyme molecule is not consumed or destroyed, but goes on to similarly “cut” other RNA molecules. During 2000,

Thomas Steitz and Peter Moore, et al., proved that ribosomes (i.e., the cell’s internal protein-synthesis “machinery”) are functionally ribozymes. See also RIBONUCLEIC

ACID (RNA), CATALYTIC RNA, BASE (NUCLEO-

TIDE), ENZYME, CELL, RIBOSOMES, CATALYST.

Ricin A lethal-to-cells protein naturally produced in castor beans. In 1994, Robert J. Ferl and Paul C. Sehnke genetically engineered a tobacco plant to produce ricin. Attached to a pharmaceutical “guided missile” or “magic bullet” such as a monoclonal antibody or the CD4 protein, ricin is potentially useful for treatment against some tumors and has been investigated as a possible treatment against acquired immune deficiency syndrome

(AIDS). See also IMMUNOTOXIN, MONOCLONAL

Roving Gene See JUMPING GENES, TRANSPOSI-

TION, TRANSPOSASE, GENE, GENOME, DEOXYRIBO-

NUCLEIC ACID (DNA).

Rps1c Gene A gene that confers to any soybean plant (possessing that gene in its DNA) resistance to several strains/races of phytophthora root rot (PRR) disease. See also

GENE, DEOXYRIBONUCLEIC ACID (DNA), SOYBEAN

PLANT, PHYTOPHTHORA ROOT ROT.

Rps1k Gene A gene that confers to any soybean plant (possessing that gene in its DNA) resistance to as many as 21 strains/races of phytophthora root rot (PRR) disease. See

also GENE, DEOXYRIBONUCLEIC ACID (DNA), PHY-

TOPHTHORA ROOT ROT, SOYBEAN PLANT.

Rps6 Gene A gene that confers to any soybean plant (possessing that gene in its DNA) resistance to some strains/races of phytophthora root rot (PRR) disease. See also GENE, DEOXY-

RIBONUCLEIC ACID (DNA), PHYTOPHTHORA ROOT

ROT, SOYBEAN PLANT.

rRNA (ribosomal RNA) The nucleic acid component of ribosomes, making up approximately two-thirds of the mass of the bacteria Escherichia coli ribosome, and approximately one-half of the mass of mammalian ribosomes. Ribosomal RNA accounts for

nearly 80% of the RNA content of the bac-

terial cell. See also NUCLEIC ACIDS, RIBOSOMES,

ESCHERICHIA COLIFORM (E. COLI), RIBONUCLEIC

ACID (RNA).

RT-PCR Acronym for Reverse Transcriptase Polymerase Chain Reaction technique. See

also REVERSE TRANSCRIPTASES, DNA POLYMERASE, POLYMERASE CHAIN REACTION (PCR),

POLYMERASE CHAIN REACTION (PCR) TECHNIQUE.

Rubitecan A pharmaceutical that either shrinks or halts the growth of pancreatic cancer tumors in humans. The pharmacophore (i.e., active portion of molecule) in rubitecan was derived from a Chinese flowering tree (Camptotheca acuminata); thus that “family” of drugs is known as camptothecins. Camptothecins inhibit a critical enzyme required for cell division to occur (thus it inhibits rapidly growing tumors). See also CANCER, PANCREAS,

TUMOR, PHARMACOPHORE, ENZYME.

Rumen (of cattle) See PREBIOTICS.

Rusts Various fungal diseases (puccinia spp.) that attack small grain plants such as wheat, corn/maize, sorghum, oats, barley and rye. Its visual appearance is like that of rust on the surfaces of those plants. See also FUNGUS,

WHEAT, CORN.

S1 Nuclease An enzyme that specifically degrades (destroys) single - stranded sequences of DNA. See also RESTRICTION

ENDONUCLEASES, ENZYME, DEOXYRIBONUCLEIC

ACID (DNA).

SAAND Acronym for Selective Apoptotic Anti-Neoplastic Drug. See also SELECTIVE

APOPTOTIC ANTI-NEOPLASTIC DRUG (SAAND).

SAGB Senior Advisory Group on Biotechnol-

ogy. See also SENIOR ADVISORY GROUP ON BIOTECHNOLOGY (SAGB).

Salicylic Acid (SA) SA is a signaling molecule in Systemic Acquired Resistance (SAR) when SAR is triggered in plants (e.g., via spray application of COBRA R herbicide to soybean plants, via spray application of harpin protein to various plants, via chewing by insects on the leaves of tomato plants, and/or the entry-into-plant of certain pathogenic bacteria/fungi, etc.). See also SYSTEMIC

ACQUIRED RESISTANCE (SAR), SIGNALING MOLE-

CULE, SOYBEAN PLANT, HARPIN, FUNGUS, PATHO-

GEN, PROTEIN, PATHOGENESIS RELATED PROTEINS,

JASMONIC ACID.

Salinity Tolerance See SALT TOLERANCE.

Salmonella A genus of bacteria, consisting of more than 2,400 serovars (strains/types) classified within two species (Salmonella enterica and Salmonella bongori). All of these serovars are potentially pathogenic (disease-causing) to humans. For example, some variants of Salmonella typhimurium can cause typhoid fever. The nontyphoid strains of Salmonella generally cause enterocolitis; although that enterocolitis can lead to more serious systemic infections. Salmonella enteritidis and Salmonella typhimurium are increasingly causing outbreaks of foodborne illnesses (e.g., when foods are not washed or cooked thoroughly enough prior to

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consumption by humans). See also BACTERIA,

PATHOGEN, PATHOGENIC, STRAIN, COMMENSAL.

Salting Out A technique used for forcing (dissolved) proteins out of a solution by increasing the concentration of salt in the solution. The Na+ and Cl– ions derived from the salt compete for and “tie up” water molecules that are solubilizing the protein molecules, thereby rendering them insoluble or more insoluble.

SAM See SAM-K GENE.

Sam-K Gene A gene naturally present within the E. coli bacteriophage T3. If the sam-k