P A T H O G E N ,

BIOLUMINES-

GROUP,

sequence) with the gene of interest. Thus, the polymorphic DNA sequences are linked to that specific gene. Their linked presence serves to facilitate genetic mapping (i.e., “location” of specific gene(s) on an organism’s genome). See also GENETIC MAP,

SEQUENCE (OF A DNA MOLECULE), RESTRICTION

FRAGMENT LENGTH POLYMORPHISM (RFLP) TECH-

NIQUE, LINKAGE, DEOXYRIBONUCLEIC ACID

(DNA), PHYSICAL MAP (OF GENOME), LINKAGE

MARKER (GENETIC MARKER), LINKAGE

MAP, TRAIT, GENOME, GENE, QUANTITATIVE TRAIT

LOCI (QTL).

RAPD See RANDOM AMPLIFIED POLYMORPHIC DNA

TECHNIQUE.

Rapid Microbial Detection (RMD) A broad term used to describe the various testing products and technologies that can be utilized to quickly detect the presence of microorganisms (e.g., pathogenic bacteria in a food processing plant). These testing products are based on immunoassay, DNA probe, electrical conductance and/or impedance, bioluminescence, and enzyme-induced reactions (e.g., which produce fluorescence or a color change to indicate the presence of specific microorganism). See also

C E N C E , M I C R O B E , B A C T E R I A ,

IMMUNOASSAY, ENZYME, PROBE, DNA PROBE,

ELECTROPHORESIS, HAZARD ANALYSIS AND CRIT-

ICAL POINTS (HACCP).

ras Gene Discovered in 1978 by Edward Scolnick, who named it ras for “rat sarcoma” (the particular diseased tissue in which he

R found it). The ras gene is also present in the human genome, and it is an oncogene that is believed to be responsible for up to 90% of all human pancreatic cancer, 50% of human colon cancers, 40% of lung cancers, and 30% of leukemias. The ras gene codes for the production (manufacture) of ras proteins, which help to signal each cell to divide and grow at appropriate time(s); e.g., when free EGF “attaches” to relevant cell receptor on the plasma membrane. When the ras gene has been damaged or mutated (e.g., via exposure to cigarette smoke or ultraviolet light, etc.), it codes for (causes to be manufactured in the cell’s ribosome) a mutated version of the ras protein that can cause the cell to become cancerous (i.e., divide and

grow uncontrollably). See also GENE, ONCO-

GENES, p53 GENE, GENETIC CODE, MEIOSIS,

DEOXYRIBONUCLEIC ACID (DNA), CARCINOGEN,

RIBOSOMES, CANCER, TUMOR, ras PROTEIN, FAR-

NESYL TRANSFERASE, PROTO-ONCOGENES, PRO-

TEIN, EPIDERMAL GROWTH FACTOR (EGF), EGF

RECEPTOR.

ras Protein A transmembrane (i.e., through the cell membrane) protein for which the ras gene codes. The ras protein end outside the cell membrane acts as a receptor for applicable growth factors (e.g., fibroblast growth factor), and conveys that signal (to divide/grow) into the cell when that chemical signal (i.e., the growth factor) touches the “receptor end” of the ras protein. When the ras gene has been damaged or mutated (e.g., via exposure to cigarette smoke or ultraviolet light), that gene causes excess ras proteins to be manufactured, which causes oversignaling of the cell to divide and grow (i.e., cell becomes cancerous). See also GENE,

TRANSMEMBRANE PROTEINS, ras GENE, FIBROBLAST GROWTH FACTOR (FGF), ONCOGENES,

GENETIC CODE, PROTEIN, p53 PROTEIN, MEIOSIS,

CARCINOGEN, RIBOSOMES, DEOXYRIBONUCLEIC ACID (DNA), CANCER, TUMOR, PROTO-ONCO- GENES, RECEPTORS, EGF RECEPTOR, CD4 PROTEIN,

SIGNALING, SIGNAL TRANSDUCTION.

Rational Drug Design T h e ‘ e n g i n e e r i n g ’ (building) of chemically synthesized drugs based on knowledge of receptor modeling and drug/target interaction(s) with the aid of supercomputers/interactive graphics/etc.; the educated, creative design of the threedimensional structure of a drug atom by atom, i.e., “from the ground up.” This approach represents a major advance over the prior practice of first synthesizing large numbers of compounds (or finding them in nature), followed by thousands of tedious screenings to test for efficacy against a given disease (target). The approach of rational drug design has, however, not yet been perfected and optimized due, in part, to gaps in our knowledge of drug/receptor interaction and to gaps in our knowledge in general. See

also RECEPTORS, RECEPTOR MAPPING (RM), ANALOGUE, MOLECULAR DIVERSITY, TARGET (OF A THERAPEUTIC AGENT), IN SILICO BIOLOGY, FREE ENERGY, IN SILICO SCREENING.

© 2002 by CRC Press LLC

RB See REFRACTILE BODIES.

RBS1 Gene A gene that confers to any soybean plant (possessing that gene in its DNA) resistance to the adverse effects of the soilborne fungus Phialophora gregata, which can cause the plant disease brown stem rot (BSR) in soybean plants. See also GENE,

DEOXYRIBONUCLEIC ACID (DNA), BROWN STEM

ROT (BSR), FUNGUS, PATHOGENIC, SOYBEAN PLANT.

RBS3 Gene A gene that confers to any soybean plant (possessing that gene in its DNA) resistance to the adverse effects of the soilborne fungus Phialophora gregata, which can cause the plant disease known as brown stem rot (BSR) in soybean plants. See also

GENE, DEOXYRIBONUCLEIC ACID (DNA), BROWN

STEM ROT (BSR), FUNGUS, PATHOGENIC, SOYBEAN

PLANT.

rDNA See RECOMBINANT DNA.

Reactive Oxygen Species See FREE RADICAL,

OXIDATION, OXIDATIVE STRESS.

Reading Frame The particular nucleotide sequence that starts at a specific point and is then partitioned into codons. The reading frame may be shifted by removing or adding a nucleotide(s). This would cause a new sequence of codons to be read. For example, the sequence CATGGT is normally read as the two codons: CAT and GGT. If another adenosine nucleotide (A) were inserted between the initial C and A, producing the sequence CAATGGT, then the reading frame would have been shifted in such a way that the two new (different) codons would be CAA and TGG, which would code for something completely different. See also

CODON, GENETIC CODE, FRAMESHIFT, DEOXYRIBO-

NUCLEIC ACID (DNA), MUTATION.

Reassociation (of DNA) The pairing of complementary single strands (of the molecule) to form a double helix (structure). See also

DOUBLE HELIX.

RecA The product of the RecA locus (in a gene of) Escherichia coli. It is a protein with dual activities, acting as a protease and also able to exchange single strands of DNA (deoxyribonucleic acid) molecules. The protease activity controls the SOS response. The nucleic acid handling facility (i.e., ability to exchange single strands of DNA) is involved in recombination/repair pathways. See also

SOS RESPONSE, LOCUS, PROTEIN, RIBOSOMES,

ESCHERICHIA COLIFORM (E. COLI).

	Receptor Fitting (RF) A research method
	used to determine the macromolecular struc-
	ture that a chemical compound (e.g., an
	inhibitor) must have in order to fit (in a lock-
	and-key fashion) into a receptor. For exam-
	ple, a pain inhibitor compound blocking a
	pain receptor on the surface of a cell. See
	also CD4 PROTEIN, T CELL RECEPTORS, RECEP-
	TORS, RECEPTOR MAPPING (RM), INTERLEUKIN-1,
	RECEPTOR ANTAGONIST (IL-1ra), RATIONAL DRUG
	DESIGN.
	Receptor Mapping (RM) A method used to
	guess at (determine) the three-dimensional
	structure of a receptor binding site extrapo-
	lating from the known structure of the mole-
	cule binding to it. This approach can be
	carried out because of the complementary
	shape of the receptor and the binding mole-
	cule. Functionally, the researcher projects the
	(guessed-at) properties of the receptor ligands
	into a mathematical model in which the pro-
	file of the receptor is predicted by comple-
	mentarity (to known chemical molecular
	structures). The receptor mapping process
	requires repetitive refinement of the mathe-
	matical model to fit properties continually
	being discovered via the use/interaction of
	chemical reagents bearing the known molec-
	ular structures. See also CD4 PROTEIN, T CELL
	RECEPTORS, RECEPTORS, RECEPTOR FITTING (RF).
	Receptor-Mediated Endocytosis See ENDOCY-
	TOSIS.
		R
	Receptors Functional proteinaceous structures
	typically found in the plasma membrane
	(surface) of cells that tightly bind specific
	molecules (organic, proteins or viruses).
	Some (relatively rare) receptors are located
	inside the cell’s membrane (e.g., free-float-
	ing receptor for Retin-A). Both (membrane,
	internal) types of receptors are a functional
	part of information transmission to the cell.
	A general overview is that once bound,
	both the receptor and its “bound entity” as
	a complex are internalized by the cell via a
	process called endocytosis, in which the cell
	membrane in the vicinity of the bound com-
	plex invaginates. This process forms a mem-
	brane “bubble” on the inside of the cell,
	which then pinches off to form an endocytic

© 2002 by CRC Press LLC

vesicle. The receptor then is released from its bound entity by cleavage in the cell’s lysosomes. It is recycled (returned) to the surface of the cell (e.g., low-density lipoprotein receptors). In some cases the receptor, along with its bound molecule, may be degraded by the powerful hydrolytic enzymes found in the cell’s lysosomes (e.g., insulin receptors, epidermal growth factor receptors, and nerve growth factor receptors).

Endocytosis (internalization of receptors and bound ligand such as a hormone) removes hormones from the circulation and makes the cell temporarily less responsive to them because of the decrease in the number of receptors on the surface of the cell. Hence the cell is able to respond (to a new signal). A receptor may be thought of as a butler who allows guests (in this case molecules that bind specifically to the receptor) to enter the house (cell) and who accompanies them as they enter.

Another mode of “reception” occurs when, following binding, a transmembrane protein (e.g., one of the G proteins) activates the portion of the transmembrane (i.e., through the cell membrane) protein lying inside the cell. That “activation” causes an effector inside the cell to produce a “signal” chemical inside the cell which causes the cell to react to the original external chemical signal (that bound itself to the receptor portion of the transmembrane protein). See also CD4

PROTEIN, T CELL RECEPTORS, RECEPTOR FITTING

R(RF), RECEPTOR MAPPING (RM), LYSOSOMES,

INTERLEUKIN-1 RECEPTOR ANTAGONIST (IL-1ra),

CD95 PROTEIN, TRANSFERRIN, VAGINOSIS, SIGNAL

TRANSDUCTION, ENDOCYTOSIS, G PROTEINS, CELL,

SIGNALING, PROTEIN, NUCLEAR RECEPTORS, HUMAN

IMMUNODEFICIENCY VIRUS TYPE 1 (HIV- 1), HUMAN

IMMUNODEFICIENCY VIRUS TYPE 2 (HIV- 2).

Recessive (gene) See RECESSIVE ALLELE.

Recessive Allele Discovered by Gregor Mendel in the 1860s, this refers to an allelic gene whose existence is obscured in the phenotype of a heterozygote by the dominant allele. In a heterozygote, the recessive allele does not produce a polypeptide; it is “switched off.” In this case, the dominant allele is the one producing the polypeptide chain (via cell’s ribosome). See also GENETICS,

ALLELE, DOMINANT ALLELE, HOMOZYGOUS, HET-

EROZYGOTE, POLYPEPTIDE (protein), CELL, RIBO-

SOMES.

Recombinant DNA (rDNA) DNA formed by the joining of genes (genetic material) into a new combination. See also RECOMBINATION,

GENETIC ENGINEERING.

Recombinant DNA Advisory Committee (RAC) The former standing U.S. national committee set up in 1974 by the U.S. National Institutes of Health (NIH) to advise the NIH director on matters regarding policy and safety issues of recombinant DNA research and development. Over time, it had evolved to become part of the American government’s regulatory process for recombinant DNA research and product approval. The RAC was terminated by the director of the NIH in 1996 because the “human health and environmental safety concerns expressed at the inception (of genetic engineering/biotechnology) had not materialized.” See also

INTERIM OFFICE OF THE GENE TECHNOLOGY

REGULATOR (IOGTR), GENE TECHNOLOGY OFFICE,

GENETIC ENGINEERING, ZKBS (CENTRAL COMMITTEE

ON BIOLOGICAL SAFETY), NATIONAL INSTITUTES

OF HEALTH (NIH), RECOMBINANT DNA (rDNA), BIO-

TECHNOLOGY, RECOMBINATION, INDIAN DEPART-

MENT OF BIOTECHNOLOGY, COMMISSION OF

BIOMOLECULAR ENGINEERING, GENE TECHNOLOGY

REGULATOR (GTR), GENETIC MANIPULATION ADVI-

SORY COMMITTEE (GMAC).

Recombinase An enzyme that acts to “cut open” the strand of DNA within a cell (e.g., to “splice-out” or “splice in”) a given gene. During 2000, Nam-Hai Chua and and Jianru Zuo showed that activation of the gene for recombinase (via β estradiol transcription factor) could be done to cause expression of recombinase in a manner that “spliced out” (removed) antibiotic-resistance “marker genes” from genetically engineered

plants. See also ENZYME, DEOXYRIBONUCLEIC ACID (DNA), GENE, CELL, GENE SPLICING, GENETIC

ENGINEERING, TRANSCRIPTION FACTORS, ANTI-

BIOTIC RESISTANCE, MARKER GENES (GENETIC

MARKER).

Recombination The joining of genes, sets of genes, or parts of genes, into new combinations, either biologically or through laboratory manipulation (e.g., genetic engineering). See

© 2002 by CRC Press LLC

also GENETIC ENGINEERING, GENE, RECOMBINANT

DNA (rDNA).

Red Blood Cells See ERYTHROCYTES. Redement Napole (RN) Gene A swine gene

that causes animals (possessing at least one negative allele of this gene) to produce meat which is more acidic than average, and thus that meat has a lower “water-holding” capacity. The RN gene was first identified in the Hampshire breed of swine in France. Since the 1960s, the Hampshire breed has been known to produce meat that is more acidic than average. See also GENE, ALLELE, ACID.

Reduction (biological) The decomposition of complex compounds and cellular structures by heterotrophic organisms. In a given ecological system, this heterotrophic decomposition serves the valuable function of recycling organic materials. This occurs because the heterotrophs absorb some of the decomposition products (for nourishment) and leave the balance of the (decomposed) substances for consumption (recycling) by other organisms. For example, bacteria break down fallen leaves on the floor of a forest, thus releasing some nutrients to be utilized by plants. See also HETEROTROPH.

Reduction (in a chemical reaction) The gain of (negatively charged) electrons by a chemical substance. When one substance is reduced by another, the other compound is oxidized (loses electrons) and is called the reducing agent. See also OXIDATION-REDUCTION

REACTION, OXIDIZING AGENT.

Redundancy A term used to describe the fact that some amino acids have more than one codon (that codes for production of that amino acid). There are approximately 64 possible codons available to code for 20 amino acids. Therefore, some amino acids will be specified by more than one codon. These (extra) codons are redundant. See also

CODON, GENETIC CODE, RIBOSOMES.

Refractile Bodies (RB) Dense, insoluble (not easily dissolved) protein bodies (i.e., clumps) produced within the cells of certain microorganisms. The refractile bodies function as a sort of natural storage device for the microorganism. They are called refractile bodies because their greater density (than the rest of the microorganism’s body mass)

causes light to be refracted (bent) when it is passed through them. This bending of light causes the appearance of very bright and dark areas around the refractile body and makes them visible under a microscope.

Relatively rare in natural occurrence, refractile bodies can be induced (caused to occur) in procaryotes (e.g., bacteria) when the procaryotes are genetically engineered to produce eucaryotic (e.g., mammal) proteins. The proteins are stored in refractile bodies. For example, the Escherichia coli bacterium can be genetically engineered to produce bovine somatotropin (BST, a cow hormone), which is stored within refractile bodies in the bacterium. After some time of growth when a significant amount of BST has been synthesized, the Escherichia coli cells are disrupted (broken open), and the refractile bodies are removed by centrifugation and washed. They are then dissolved in appropriate solutions to release the protein molecules. This step denatures (unfolds, inactivates) the BST molecules and they are refolded to their native conformation (i.e., restored to the natural conformation found within the cow) in order to regain their natural activity. The protein is then formulated in such a way as to be commercially viable as a biopharmaceutical.

Refractile bodies are also known as inclusion bodies, protein inclusion bodies, and refractile inclusions.

One point of interest is that the prerequisite

for the generation of a mammalian protein by R (in) a living foreign system such as E. coli is

that the system used to generate the protein

(1) must not have an immune system capable of destroying the foreign protein it is making, or (2) the foreign protein made must be camouflaged or protected from any defense mechanisms possessed by the synthesizing

organism. See also PROTEIN, GENETIC ENGINEERING, GENETIC CODE, PROCARYOTES, EUCARYOTE,

ESCHERICHIA COLIFORM (E. COLI), BOVINE SOMA-

TOTROPIN (BST), ULTRACENTRIFUGE, CONFORMA-

TION, NATIVE CONFORMATION, PROTEIN FOLDING.

Regulatory Enzyme A highly specialized enzyme having a regulatory (controlling) function through its capacity to undergo a change in its catalytic activity. There exist

© 2002 by CRC Press LLC