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For example, the cytokines stimulate the endothelial cells to express (synthesize and present) P-selectins and E-selectins on the internal surfaces (of blood vessels). These selectins protrude into the bloodstream, which causes passing white blood cells (leu- kocytes) to adhere to the selectins, then leave the bloodstream by “squeezing” between adjacent endothelial cells. Cytokines are exemplified by the interferons. See also INTERLEUKIN - 1 ( IL - 1 ), LYMPHOKINES , INTERFER- ONS , GLYCOPROTEIN , PROTEIN , T CELLS , INTER- L E U K I N - 6 ( I L - 6 ), M A C R O P H A G E , L E C T I N S , FIBROBLASTS , HORMONE , ENDOTHELIAL CELLS , ENDOTHELIUM , SELECTINS , P - SELECTIN , ELAM - 1 , LEUKOCYTES , ADHESION MOLECULE . Cytolysis The dissolution of cells, particularly by destruction of their surface membranes. See also LYSIS , CECROPHINS , LYSOZYME , MAGAI- NINS , COMPLEMENT , COMPLEMENT CASCADE . Cytomegalovirus (CMV) A virus that infects different groups of people in varying amounts, depending on their behavior. For example, 40–90% of American heterosexu- als, and about 95% of homosexuals are infected with CMV. CMV normally pro- duces a latent (nonclinical, nonobvious) infection, but with AIDS or other events can cause immune system suppression. CMV produces a febrile (fever-causing) illness that is usually mild in nature but can become retinitis (eye infection). CMV can be treated (to halt life- and sight-threatening infection) in immunocompromised patients (i.e., trans- plant patients and AIDS victims) with Ganci- clovir™, an antiviral compound developed by Syntex or Foscarnet™, a compound devel- oped by Astra Pharmaceuticals. In 1996, Stephen E. Epstein found that latent CMV may cause changes in artery wall cells that aid clogging of arteries in adults (especially fol- lowing balloon angioplasty). See also VIRUS , ACQUIRED IMMUNE DEFICIENCY SYNDROME ( AIDS ). Cytopathic Damaging to cells. Cytoplasm The protoplasmic contents of the cell not including the nucleus. See also NUCLEUS , CELL , PROTOPLASM , CYTOPLASMIC DNA , PLASMA MEMBRANE , MITOCHONDRIA , CHLOROPLASTS . Cytoplasmic DNA The DNA within an organ- ism (e.g., plant) that is not inside the cell’s nucleus. Cytoplasmic DNA (i.e., located in the cell’s mitochondria and the chloroplasts) is not transferred from plant to plant via pollen, as nuclear DNA is. See also DEOXYRIBONUCLEIC ACID ( DNA ), ORGANISM , CELL , CYTOPLASM , © 2002 by CRC Press LLC C NUCLEUS , MITOCHONDRIA , MITOCHONDRIAL DNA , CHLOROPLASTS . Cytoplasmic Membrane See PLASMA MEM- BRANE . Cytosine A pyrimidine occurring as a funda- mental unit (one of the bases) of nucleic acids. See also NUCLEIC ACIDS , BASE ( NUCLEOTIDE ). Cytotoxic Poisonous to cells. Cytotoxic Killer Lymphocyte See CYTOTOXIC T CELLS . Cytotoxic T Cells Also called killer T cells. T cells that have been created by stimulated helper T cells. The T refers to cells of the cellular system rather than to cells of the humoral system (B cells). Cytotoxic T cells detect and destroy infected body cells by use of a special type of protein. The protein attaches to the infected cell’s membrane and forms holes in it. This allows the uncon- trolled leakage of ions out of, and water into, the cell, causing cell death. In general, the loss of the integrity of the cell membrane leads to death. The cytotoxic T cells also transmit a signal to the (leaking) infected cells that causes the cell to “chew up” its DNA. This includes its own DNA as well as that of the virus. See also CECROPHINS , MAGAI- NINS , INTERLEUKIN- 4 ( IL- 4 ), HELPER T CELLS ( T 4 CELLS ), VIRUS , T CELLS , SUPPRESSOR T CELLS , PROTEIN , INTERLEUKIN -2 ( IL -2 ), DEOXYRIBONU- CLEIC ACID ( DNA ), PLASMA MEMBRANE , INSULIN - DEPENDENT DIABETES MELLITIS . © 2002 by CRC Press LLC 0-8493-XXXX-X/01/$0.00+$1.50 © 2001 by CRC Press LLC D D ⌬ 12 Desaturase One of the desaturases (enzymes). See also DELTA 12 DESATURASE , COSUPPRESSION , ENZYME , DESATURASE . ␦ Endotoxins See DELTA ENDOTOXINS . ∆∆∆∆ 15 Desaturase One of the desaturases (enzymes). See also ENZYME , DESATURASE , DELTA 12 DESATURASE . D Loop A region within mitochondrial DNA in which a short stretch of RNA is paired with one strand of DNA, displacing the orig- inal partner DNA strand in this region. The same term is used to describe the displace- ment of a region of one strand of duplex DNA by a single-stranded invader in the reaction catalyzed by RecA protein. Daffodil Rice See GOLDEN RICE . Daffodils Refers to the approximately 80 species of flowering plants within the genus Narcis- sus. Native to southern Europe and northern Africa, they are the source of “golden rice” and the Alzheimer’s disease treatment com- pound galantamine hydrobromide. See also GOLDEN RICE , ALZHEIMER ’ S DISEASE . Daidzein See ISOFLAVONES . Daidzen See ISOFLAVONES . Daidzin The β-glycoside form (isomer in which glucose is attached to the molecule at the seven position of the A ring) of the isofla- vone known as daidzein (aglycone form). See also ISOFLAVONES , ISOMER , DAIDZEIN . Dalton A unit of mass very nearly equal to that of a hydrogen atom (precisely equal to 1.0000 on the atomic mass scale). Named after John Dalton (1766–1844), who devel- oped the atomic theory of matter. It is 1.660 × 10 –24 gram. See also KILODALTON ( K d ). DBT An acronym used by some to designate the Indian Department of Biotechnology. See also INDIAN DEPARTMENT OF BIOTECHNOLOGY . Deamination The removal of amino groups from molecules (e.g., in an animal’s food) via the energy-consuming metabolism of excess amino acids eaten by that animal. For example, when livestock are fed more lysine (amino acid) than their body needs in a given day (animals’ bodies can only utilize the e s s e n t i a l a m i n o a c i d s i n p r e c i s e amounts/ratios of their daily diet), the excess lysine is metabolized to urea and then excreted. See also METABOLISM , AMINO ACID , ESSENTIAL AMINO ACIDS , LYSINE ( lys ), IDEAL PRO- TEIN , “ IDEAL PROTEIN ” CONCEPT , PDCAAS , ACC SYNTHASE . Defective Virus A virus that, by itself, is unable to reproduce when infecting its host (cell), but that can grow in the presence of another virus. The other virus provides the necessary molecular machinery that the first virus lacks. Defensins A class of peptides that inhibits cer- tain fungal diseases. These are produced as a natural defense by some plants. For exam- ple, the alfalfa plant produces a defensin known as alfAFP (alfalfa antifungal pep- tide). In addition to protecting the plant from certain diseases, the alfAFP also inhibits a fungal disease known as potato early dying complex (also called Verticillium wilt), which is caused by the fungus Verticillium dahliae. See also PEPTIDE , FUNGUS . Degenerate Codons Two or more codons that code for the same amino acid. For example, isoleucine is specified by the AUU, AUC, and AUA triplets. Since in this case more than one triplet codes for isoleucine, the codons are called degenerate. See also GENETIC CODE , CODON . Dehydrogenases Enzymes that catalyze the removal of pairs of hydrogen atoms from © 2002 by CRC Press LLC D their substrates. See also SUBSTRATE ( CHEMI- CAL ), GLUTAMATE DEHYDROGENASE , ENZYME , DEHYDROGENATION . Dehydrogenation The removal of hydrogen atoms from molecules. When those mole- cules are the components of vegetable oils/fats, a lower content percentage of sat- urated fats results. See also FATS , MONOUN- SATURATED FATS , SATURATED FATTY ACIDS ( SAFA ), FATTY ACID . Deinococcus radiodurans A species of bacte- ria capable of surviving 1.5 million rads of gamma radiation (3000 times the lethal radi- ation dose for humans), surviving long peri- ods of dehydration, and surviving high doses of ultraviolet radiation. Deinococcus radio- durans was discovered in 1956 in some canned meat. See also BACTERIA , EXTREMO- PHILIC BACTERIA . Delaney Clause Formerly part of American federal law (1959 Delaney amendment to the Food, Drug and Cosmetic Act), it was elim- inated in 1996. The Delaney Clause had set a zero-risk tolerance level for carcinogenic pesticide residues in processed foods. See also CARCINOGEN . Deletions Loss of a section of the genetic material from a chromosome. The size of a deleted material can vary from a single nucleotide to sections containing a number of genes. See also GENE , CHROMOSOMES . Delta 12 Desaturase A n e n z y m e p r e s e n t within the soybean plant and in other oilseed crops (canola, maize/corn, etc.). Delta 12 desaturase ( ∆12) is involved in the synthesis “pathway” utilized by oilseed crops to syn- thesize (manufacture) polyunsaturated fatty acids (e.g., linoleic acid) from monounsat- urated fatty acids (e.g., oleic acid) in seeds (while those seeds are developing). See also ENZYME , DESATURASE , FATTY ACID , UNSATUR- ATED FATTY ACID , MONOUNSATURATED FATTY ACIDS ( MUFA ), POLYUNSATURATED FATTY ACIDS ( PUFA ), PATHWAY , OLEIC ACID , LINOLEIC ACID , SOYBEAN PLANT , CORN , CANOLA . Delta Endotoxins See CRY PROTEINS , PROTEIN . Denaturation The loss of the native conforma- tion of a macromolecule resulting, for instance, from heat, extreme pH (i.e., by acid- ity or basicity) changes, chemical treatment, etc. It is accompanied by loss of biological activity. See also CONFORMATION , CONFIGURA- TION , MACROMOLECULES . Denatured DNA DNA converted from dou- ble-stranded to single-stranded form by a denaturation process such as heating the DNA solution. In the case of heat denatur- ation, the solution becomes very gelatinous and viscous. See also DENATURATION , DEOXY- RIBONUCLEIC ACID ( DNA ), DUPLEX . Denaturing Gradient Gel Electrophoresis See D E N A T U R I N G P O L Y A C R Y L A M I D E G E L ELECTROPHORESIS . Denaturing Polyacrylamide Gel Electro- phoresis The use of PAGE (polyacrylamide gel electrophoresis) in order to separate and analyze DNA fragments (sequences) after that DNA is first denatured. This methodol- ogy can be employed to scan DNA in order to detect point mutations. See also POLYACRYLAMIDE GEL ELECTROPHORESIS ( PAGE ), POINT MUTATION , DENATURING GRADIENT GEL ELECTROPHORESIS , DEOXYRIBONUCLEIC ACID ( DNA ), DENATURED DNA , BASE EXCISION SEQUENCE SCANNING ( BESS ). Dendrimers Polymers (i.e., molecules com- posed of repeating atomic units within the molecule) that repeatedly branch (while “growing” due to addition of more atoms in a repeating pattern) until that branching is stopped by the physical constraint of con- tacting itself (i.e., having formed a complete, hollow sphere). Discovered during the 1970s by Donald Tomalia, dendrimers possess sites on their exterior surface to which genetic material (e.g., genes or other portions of DNA) can be “attached.” Dendrimers bear- ing such genetic material have shown the capacity to successfully transfer that genetic material into more than thirty types of living animal cells. See also POLYMER , DENDRITIC POLYMERS , GENE , GENETIC ENGINEERING , GENE DELIVERY , INFORMATIONAL MOLECULES , CODING SEQUENCE , TUMOR - SUPPRESSOR GENES , DEOXY- RIBONUCLEIC ACID ( DNA ), GENETIC TARGETING , GENETICS . Dendrites Highly branched structures that extend from the (nucleus of) neurons to (syn- apse junctions with) other neurons (e.g., in human brain tissue). The primary purpose of dendrites is to process signals that are gen- erated/received at the synapses (e.g., from © 2002 by CRC Press LLC D the dendrites of adjoining neurons). Neuron ribosomes are located in the dendritic spines, the dendrite projections that form synapses (the junctions between dendrites where “sig- nal transfer” between neurons takes place). Thus, those ribosomes make the proteins that are crucial to learning and memory (e.g., accomplished via growth/changes of den- drites). Messenger RNAs are synthesized (manufactured) in the nucleus of the neuron, then transported on microtubules (filaments within the neuron cell) to the ribosomes in the dendrites, where they cause manufacture of proteins (e.g., enzymes) in response to synapse activity (i.e., signals). See also NEU- RON , CELL , NEUROTRANSMITTER , RIBOSOMES , PROTEIN , ENZYME , MESSENGER RNA ( m RNA ), MICROTUBULES . Dendritic Cells These are rare white blood cells, which act to stimulate the human immune system (T cells) to combat certain types of cancer. See also CELL , IMMUNE RESPONSE , CANCER , LEUKOCYTES . Dendritic Langerhans Cells A type of cell, located in the mucous membranes of the mouth and genital areas, that permits the human immunodeficiency virus (the virus that causes AIDS) to enter and infect the body, even when there are no cuts or abra- sions through those mucous membranes. See also HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 ( HIV- 1 ), HUMAN IMMUNODEFICIENCY VIRUS TYPE 2 ( HIV- 2 ), ACQUIRED IMMUNE DEFICIENCY SYNDROME ( AIDS ), ADHESION MOLECULE , DEN- DRITIC POLYMERS . Dendritic Polymers Polymers (i.e., molecules composed of repeating atomic units within the molecule) that repeatedly branch (while “growing” due to the addition of more atoms in a repeating pattern) until that branching is stopped (e.g., by physical constraints, for those polymers within living tissues). In the absence of physical constraints, dendritic polymers can continue branching (and grow- ing) until they form a complete (hollow) sphere. Such spheres are potentially useful for protecting and “delivering” a fragile pharma- ceutical molecule to specific tissue(s) within the body. See also POLYMER , DENDRIMERS . Denitrification The process (i.e., internal res- piration) by which denitrifying bacteria (e.g., in soil) convert nitrates to gaseous nitrogen/nitrous oxide, which then enters the atmosphere. See also NITRATES , BACTERIA , RESPIRATION . Denitrification Reduction of nitrate to nitrites or into gaseous oxides of nitrogen, or even into free nitrogen by organisms. See also REDUCTION ( IN A CHEMICAL REACTION ). Denitrifying Bacteria See DENITRIFICATION . Deoxynivalenol A mycotoxin (toxin that is naturally produced by a fungus under certain conditions) which, under specific tempera- ture and moisture conditions, is sometimes produced by certain fungi (e.g., some Fusar- ium) growing in some grains (e.g., corn/maize). Deoxynivalenol is also known as DON, and/or “vomitoxin,” because certain animals (especially swine) will often vomit after they have consumed grain that contains deoxynivalenol due to its toxicity. See also TOXIN , DON , MYCOTOXINS , FUNGUS , FUSARIUM . Deoxyribonucleic Acid (DNA) D i s c o v e r e d by Frederick Miescher in 1869, DNA is the chemical basis for genes. The chemical building blocks (molecules) of which genes (i.e., paired nucleotide units that code for a protein to be produced by a cell’s machinery, such as its ribosomes) are constructed. Every inherited characteristic has its origin some- where in the code of the organism’s comple- ment of DNA. The code is made up of subunits, called nucleic acids. The sequence of the four nucleic acids is interpreted by certain molecular machines (systems) to produce the required proteins of which the organism is composed. The structure of the DNA molecule was elucidated in 1953 by James Watson, Francis Crick, and Maurice Wilkins. The DNA mol- ecule is a linear polymer made up of deox- yribonucleotide repeating units (composed of the sugar 2-deoxyribose, phosphate, and a purine or pyrimidine base). The bases are linked by a phosphate group, joining the 3 ′ position of one sugar to the 5 ′ position of the next sugar. Most molecules are double- stranded and anti-parallel, resulting in a right-handed helix structure that is held together by hydrogen bonds between a purine on one chain and pyrimidine on the other chain. DNA is the carrier of genetic © 2002 by CRC Press LLC D information, which is encoded in the sequence of bases; it is present in chromo- somes and chromosomal material of cell organelles such as mitochondria and chloro- plasts, and also present in some viruses. See also A - DNA , B - DNA , c DNA , Z - DNA , TRANSCRIP- TION , ANTIPARALLEL , DOUBLE HELIX , MESSENGER RNA ( m RNA ), NUCLEOTIDE , PROTEIN , RIBOSOMES , GENETIC CODE , GENE , CHROMOSOMES , CHROMA- TIDS , CHROMATIN , MITOCHONDRIAL DNA , CYTO- PLASMIC DNA , NUCLEAR DNA . Deprotection (of a peptide) See also HF CLEAV- AGE . Desaturase An enzyme (group) family that is present within the soybean plant and other oilseed crops (e.g., canola, corn/maize). One or more desaturases is involved in the synthe- sis “pathway” through which oilseed crops produce unsaturated fatty acids (e.g., linoleic acid). A desaturase is also involved in produc- tion of beta carotene (in some plants). See also ENZYME , FATS , STEAROYL - ACP DESATURASE , DELTA 12 DESATURASE , SOYBEAN PLANT , PATH- WAY , LINOLEIC ACID , FATTY ACID , UNSATURATED FATTY ACID , GOLDEN RICE , BETA CAROTENE . Desferroxamine Manganese An iron chelat- ing agent (i.e., it chemically binds to iron atoms in the blood, thus trapping the iron atoms). The molecule also acts as an hSOD mimic by capturing harmful oxygen free radicals in the blood before they damage the walls of blood vessels. Recent research indi- cates that desferroxamine manganese may be useful in blocking the onset of cataracts. See also HUMAN SUPEROXIDE DISMUTASE ( h SOD ), XANTHINE OXIDASE , LAZAROIDS . Desulfovibrio A genus of bacteria that reduces sulfate to H 2 S (hydrogen sulfide). Energy is obtained by oxidation of H 2 or organic molecules. Not a strict autotroph because CO 2 cannot be used as a sole carbon source. See also REDUCTION ( IN A CHEMICAL REACTION ), AUTOTROPH . Dextran A polysaccharide produced by yeasts and bacteria as an energy storage reservoir (analogous to fat in humans). Consists of glu- cose residues, joined almost exclusively by alpha-1,6 linkages. Occasional branches (in the molecule) are formed by alpha 1,2, alpha 1,3, or alpha 1,4 linkages. Which linkage is used depends on the species of yeast or bac- teria producing the dextran. See also POLYSACCHARIDES . Dextrorotary (D) Isomer A stereoisomer that rotates the plane of plane-polarized light to the right. Dextro means right. See also STEREO- ISOMERS , LEVOROTARY ( L ) ISOMER , POLARIMETER . DHA See DOCOSAHEXANOIC ACID ( DHA ). Diabetes A grouping of diseases in which the body either does not synthesize (manufac- ture) insulin, or else its tissues are insensitive to the insulin that it does synthesize. Approximately 5–10% of all people with diabetes are unable to synthesize insulin (e.g., because their insulin-making tissue was destroyed by autoimmune disease). Approximately 90–95% of all people with diabetes are insensitive to the insulin their body synthesizes. See also PANCREAS , INSULIN , INSULIN - DEPENDENT DIABETES MELLITIS ( IDDM ), AUTOIMMUNE DISEASE , BETA CELLS , N- 3 FATTY ACIDS , CALPAIN- 10 , TYPE I DIABETES , TYPE II DIA- BETES , HAPTOGLOBIN . Diacylglycerols Molecules that consist of two fatty acids attached to a glycerol “backbone.” Research during the 1990s indicated that consumption of vegetable oils (e.g., used in frying foods) containing primarily diacyl- glycerols (versus typical triacylglycerols), is less likely to result in it being deposited as body fat (adipose tissue). See also FATTY ACID , SATURATED FATTY ACIDS ( SAFA ), UNSATURATED FATTY ACID , ADIPOSE , TRIACYLGLYCEROLS . Diadzein See DAIDZEIN , ISOFLAVONES . Dialysis The separation of low molecular weight compounds from high molecular weight components in solution by diffusion through a semipermeable membrane. Fre- quently utilized to remove salts and biolog- ical effectors (such as nicotinamide adenine dinucleotides, nucleotide phosphates, etc.) from polymeric molecules such as protein, DNA, or RNA. Commonly used membranes have a molecular weight cutoff (threshold) of around 10,000 Daltons, but other mem- brane pore sizes are available. See also HOL- LOW FIBER SEPARATION , ACTIVE TRANSPORT . Diamond vs. Chakrabarty See CHAKRABARTY DECISION . © 2002 by CRC Press LLC D Diastereoisomers Four variations of a given molecule, consisting of a pair of stereoiso- mers about a second asymmetric carbon atom for each of the two isomers of the first asymmetric carbon atom. See also STEREO- ISOMERS , CHIRAL COMPOUND . Differentiation Refers to processes by which a single type of cells (stem cells, embryonic stem cells, etc.) become multiple, different types of (specialized) cells. See also CELL , STEM CELLS , STEM CELL ONE , STEM CELL GROWTH FACTOR ( SCF ), TOTIPOTENT STEM CELLS , COLONY STIMULATING FACTORS ( CSF s ), EMBRYONIC STEM CELLS , HUMAN EMBRYONIC STEM CELLS , GRANU- LOCYTE - MACROPHAGE COLONY STIMULATING FACTOR ( GM - CSF ), HEDGEHOG PROTEINS . Digestion (within chemical production plants) Breakdown of feed stocks by various processes (chemical, mechanical, and biolog- ical) to yield their desired building-block com- ponents for inclusion as raw materials in subsequent chemical or biological processes. Digestion (within organisms) The enzyme- enhanced hydrolysis (breakdown) of major nutrients (food) in the gastrointestinal sys- tem to yield their building-block compo- nents (to the organism), such as amino acids, fatty acids, or other essential nutrients. See also HYDROLYSIS , FATS , PROTEIN , AMINO ACID , ESSENTIAL AMINO ACIDS , ESSENTIAL NUTRIENTS , FATTY ACID , ESSENTIAL FATTY ACIDS , LIPASE , “ IDEAL PROTEIN ” CONCEPT , ENZYME , PROTEASES , PROTEOLYTIC ENZYMES , ABSORPTION , TRYPSIN , LECITHIN , PROTEIN DIGESTIBILITY - CORRECTED AMINO ACID SCORING ( PDCAAS ). Diglycerides See TRIGLYCERIDES . Diphtheria Antitoxin Discovered by Emil von Behring in 1900. See also ANTITOXIN , ENTEROTOXIN . Diploid The state of a cell in which each of the chromosomes, except for the sex chro- mosomes, is always represented twice (46 chromosomes in humans). In contrast to the haploid state in which each chromosome is represented only once. See also DIPLOPHASE , CHROMOSOMES , HOMOZYGOUS , TRIPLOID . Diplophase A phase in the life cycle of an organism in which the cells of the organism have two copies of each gene. When this state exists the organism is said to be diploid. See also DIPLOID , GENE , HOMOZYGOUS , CELL . Direct Transfer Refers to methods of insert- ing a gene directly into a cell’s DNA without the use of a vector. One example of direct transfer is electroporation. See also GENE , GENETIC ENGIEERING , VECTORS , CELL , DEOXY- RIBONUCLEIC ACID ( DNA ), ELECTROPORATION . Directed Self-Assembly See SELF - ASSEMBLY ( OF A LARGE MOLECULAR STRUCTURE ). Disaccharides Carbohydrates consisting of two covalently linked monosaccharide units; hence di for two. See also OLIGOSACCHARIDES , MONOSACCHARIDES , POLYSACCHARIDES . Dissimilation The breakdown of food material to yield energy and building blocks for cel- lular synthesis. See also DIGESTION ( WITHIN ORGANISMS ). Dissociating Enzymes See HARVESTING ENZYMES . Distribution See “ ADME ” TESTS , PHARMACOKI- NETICS . Disulfide Bond An important type of covalent bond formed between two sulfur atoms of dif- ferent cysteines in a protein. Disulfide bonds (linkages, bridges) contribute to holding pro- teins together and also help provide the inter- nal structure (conformation) of the protein. See also PROTEIN , CYSTEINE ( cys ), CYSTINE . Diversity (within a species) R e f e r s t o t h e genetic variation that exists within a popula- tion (of organisms) in a species. For example, black cattle and white cattle; or both toxic and nontoxic strains/serotypes of Escherichia coliform (E. coli) bacteria. This diversity is due to one or more single-nucleotide poly- morphisms (SNPs) in each individual’s genome (DNA) within the population of organisms. See also SPECIES , SINGLE - NUCLE- OTIDE POLYMORPHISMS ( SNP s ), POLYMORPHISM ( GENETIC ), NUCLEOTIDE , ORGANISM , STRAIN , SEROTYPES , ESCHERICHIA COLIFORM ( E . COLI ), ESCHERICHIA COLIFORM 0157 : H 7 ( E . COLI 0157 : H 7 ). Diversity Biotechnology Consortium A non- profit U.S. organization formed in August of 1994 by a group of research institutions and companies. The consortium’s first president was Stuart A. Kauffman of the Santa Fe Institute. The consortium’s purpose is to fur- ther the use of molecular diversity as a tool in drug design, and in the study of mutating © 2002 by CRC Press LLC D viruses. See also MOLECULAR DIVERSITY , RATIONAL DRUG DESIGN , DIVERSITY ESTIMATION ( OF MOLECULES ), MOLECULAR BIOLOGY , VIRUS , MUTATION , MUTANT , SITE - DIRECTED MUTAGENE- SIS ( SDM ), COMBINATORIAL CHEMISTRY , COMBI- NATORIAL BIOLOGY . Diversity Estimation (of molecules) See COM- BINATORIAL CHEMISTRY . DNA See DEOXYRIBONUCLEIC ACID ( DNA ). DNA Analysis See DNA PROFILING . DNA Bridges Large segments of DNA whose sequence (i.e., composition) is known and mapped in total. Those sequences are then utilized by scientists to piece together (bridging the DNA segments) and assemble a (more) complete map (e.g., of an organ- ism’s chromosome or genome). See also DEOXYRIBONUCLEIC ACID ( DNA ), GENETIC MAP , SEQUENCE ( OF A DNA MOLECULE ), CHROMOSOME , GENOME , SEQUENCE MAP , SHOTGUN SEQUENCING . DNA Chimera One DNA molecule composed of DNA from two different species. See also CHIMERA . DNA Chip See BIOCHIPS , GENE EXPRESSION ANALYSIS , PROTEOMICS . DNA Fingerprinting See DNA PROFILING . DNA Ligase An enzyme that creates a phos- phodiester bond between the 3 ′ end of one DNA segment and the 5 ′ end of another, while they are base-paired to a template strand. The enzyme seals (joins) the ends of single-stranded DNA in a duplex DNA chain. DNA ligase constitutes a part of the DNA repair mechanism available to the cell. See also NICK , LIGASE , DEOXYRIBONUCLEIC ACID ( DNA ), GENE REPAIR ( NATURAL ), DUPLEX . DNA Marker See MARKER ( DNA MARKER ). DNA Methylation Refers to a DNA molecule that is saturated with methyl groups (i.e., methyl submolecule groups CH 3 have attached themselves to the DNA molecule’s “backbone” at all possible locations on that DNA molecule). DNA methylation is used by healthy cells to turn off certain genes when those particular genes are no longer needed (e.g., turn off genes involved in juve- nile development after organism reaches adulthood). DNA methylation (of cell genes that would normally prevent inappropriate cell division/proliferation) also occurs in some cancers. See also DEOXYRIBONUCLEIC ACID ( DNA ), METHYLATED , CELL , GENE , CANCER , TRANSCRIPTION , GENETIC CODE , MESSENGER RNA ( m RNA ), p53 GENE , TUMOR - SUPPRESSOR GENES . DNA Microarray Initially developed by Patrick Brown during the 1980s, these microarrays enable analysis of the levels of expression of genes in an organism, or com- parison of gene expression levels (e.g., between diseased and nondiseased tissues) via hybridization of messenger RNA (mRNA) to its counterpart DNA sequence, when biological samples containing DNA (e.g., in liquid) are passed over the array sur- face. To manufacture the DNA microarray, cellular mRNA is used to make segments of complementary DNA (cDNA) in lengths of approximately 500–5000 base pairs long, using the reverse transcriptase polymerase chain reaction (RT-PCR). These cDNA seg- ments are then attached to a nylon or glass surface at known spots, so when hybridiza- tion-of-sample-DNA occurs, the location of the spot tells what DNA was in the sample. Another way to manufacture a type of DNA microarray is to similarly attach oligonucle- otides or peptide nucleic acids of known sequence (composition) at known spots on the nylon or glass surface, and pass the biological sample containing DNA (e.g., in liquid) over that surface to identify the DNA in the sample by the spot to which it hybridizes. See also GENE , ORGANISM , BIOCHIPS , MICROFLUIDICS , DEOXYRIBONUCLEIC ACID ( DNA ), MESSENGER RNA ( m RNA ), HYBRIDIZATION ( MOLECULAR GENETICS ), EXPRESS , GENE EXPRESSION ANALYSIS , PROTEOM- ICS , MICROARRAY ( TESTING ), OLIGONUCLEOTIDE , NUCLEIC ACIDS , SEQUENCE ( OF A DNA MOLECULE ), BIOINFORMATICS . DNA Polymerase An enzyme that catalyzes the synthesis of DNA. The process is accom- plished by catalyzing the addition of deox- yribonucleotide residues to the free 3 ′- hydroxyl end of a DNA chain, starting from a mixture of the appropriate triphosphory- lated bases, which are dATP, dGTP, dCTP, and dTTP. This chemical reaction is revers- ible and, hence, DNA polymerase also func- tions as an exonuclease. See also ENZYME , EXONUCLEASE , TAQ DNA POLYMERASE , DEOXY- RIBONUCLEIC ACID ( DNA ), SYNTHESIZING ( OF DNA MOLECULES ). © 2002 by CRC Press LLC D DNA Probe Also called gene probe or genetic probe. Short, specific (complementary to desired gene) artificially-produced segments of DNA are used to combine with and detect the presence of specific genes (or shorter DNA segments) within a chromosome. If a DNA probe of known composition and length is mingled with pieces of DNA (genes) from a chromosome, the probe will cling to its exact counterpart in the chromo- somal DNA pieces (genes), forming a stable double-stranded hybrid. The presence of this (now) “labeled” probe is detected visually or with the aid of another detection instru- ment. Because the composition of the DNA probes is known, scientists can riffle through a chromosome, spotting segments of DNA (i.e., genes) that seem to be linked to genetic diseases. See also MUSCULAR DYSTROPHY ( MD ), PROBE , POLYMERASE CHAIN REACTION ( PCR ), GENE , POLYMERASE CHAIN REACTION ( PCR ) TECH- NIQUE , CHROMOSOMES , DOUBLE HELIX , DUPLEX , H Y B R I D I Z A T I O N ( M O L E C U L A R G E N E T I C S ), HYBRIDIZATION SURFACES , DEOXYRIBONUCLEIC ACID ( DNA ), HOMEOBOX , RAPID MICROBIAL DETECTION ( RMD ), SOUTHERN BLOT ANALYSIS . DNA Profiling Invented in 1985 by Alec Jef- freys, this technique is used by forensic (i.e., crime-solving) chemists to match biological evidence (e.g., a blood stain) from a crime scene to the person (e.g., the assailant) involved in that particular crime. DNA pro- filing involves the use of RFLP (restriction fragment length polymorphism) analysis or ASO/PCR (allele-specific oligonucle- otide/polymerase chain reaction) analysis to identify the specific sequence of bases (i.e., nucleotides) in a piece of DNA taken from the biological evidence. Since the specific sequence of bases in DNA molecules is dif- ferent for each individual (due to DNA poly- morphism), a criminal’s DNA can be matched to that of the evidence to prove guilt or innocence. Biological evidence may include, among other things, blood, hair, nail fragments, skin, and sperm. See also DEOXY- RIBONUCLEIC ACID ( DNA ), RESTRICTION FRAG- MENT LENGTH POLYMORPHISM ( RFLP ) TECHNIQUE , POLYMORPHISM ( CHEMICAL ), POLYMERASE CHAIN REACTION ( PCR ) TECHNIQUE , ALLELE , NUCLEO- TIDE , NUCLEIC ACIDS , OLIGOMER , GENETIC CODE , INFORMATIONAL MOLECULES , OLIGIONUCLE- OTIDE , CODON . DNA Synthesis See SYNTHESIZING ( OF DNA MOL- ECULES ). DNA Typing See DNA PROFILING . DNA Vaccines Products in which “naked” genes (i.e., pieces of bare DNA) are used to stimulate an immune response (e.g., either a cellular immune response, humoral immune response, or otherwise raise antibodies against the patho- gen from which the naked genes have arisen or been derived). See also DEOXYRIBONUCLEIC ACID ( DNA ), IMMUNE RESPONSE , CELLULAR IMMUNE RESPONSE , HUMORAL IMMUNITY , ANTIBODY , “ NAKED ” GENE , PATHOGEN , DNA VECTOR . DNA Vector A vehicle (such as a virus) for transferring genetic information (DNA) from one cell to another. See also BACTE- RIOPHAGE , RETROVIRUSES , VECTOR . DNA-Dependent RNA Polymerase See RNA POLYMERASE . DNA-RNA Hybrid A double helix that con- sists of one chain of DNA hydrogen bonded to a chain of RNA by means of complemen- tary base pairs. See also HYBRIDIZATION ( MOLECULAR GENETICS ), HYBRIDIZATION ( PLANT GENETICS ), DOUBLE HELIX . DNAse Deoxyribonuclease, an endonuclease enzyme family that degrades (cuts up) DNA molecules. DNase I is produced and secreted by the salivary glands, intestines, liver, and pancreas of animals. It has optimal activity (i.e., greatest ability to cut up DNA molecules) at neutral pH (neither acidic nor basic). DNase II has optimal activity between pH 4.6 and 5.5 (i.e., in slightly acidic solutions). See also ENZYME , DEOXYRIBONUCLEIC ACID ( DNA ), ENDO- NUCLEASES , PANCREAS , ACID , BASE ( GENERAL ). Docosahexanoic Acid (DHA) O n e o f t h e omega-3 (n-3) highly unsaturated fatty acids (HUFA), DHA is important in the develop- ment of the human infant’s brain, spinal cord, and retina tissues. DHA aids optimal brain and nervous system development in human infants, and is required for optimal brain function throughout life. Naturally present in human breast milk and fish oil. The human body converts linolenic acid (e.g., from consumption of soybean oil) to the two highly unsaturated fatty acids (HUFA) docosahexanoic acid (DHA) and © 2002 by CRC Press LLC D eicosapentanoic acid (EPA). Research indi- cates that consumption of docosahexanoic acid also helps to reduce the risk of heart disease (by lowering blood pressure) and depression (via its effect in the brain). See also POLYUNSATURATED FATTY ACIDS ( PUFA ), HIGHLY UNSATURATED FATTY ACIDS ( HUFA ), N- 3 FATTY ACIDS , FATTY ACIDS , UNSATURATED FATTY ACIDS , ESSENTIAL FATTY ACIDS , LINOLENIC ACID , SOYBEAN OIL , EICOSANOIDS , EICOSAPENTANOIC ACID ( EPA ). Domain (of a chromosome) May refer either to a discrete structural entity defined as a region within which supercoiling is independent of other domains, or to an extensive region, including an expressed gene that has height- ened sensitivity to degradation by the enzyme DNAse I. See also GENE , EXPRESS , ENZYME . Domain (of a protein) A discrete continuous Download 4.84 Kb. Do'stlaringiz bilan baham: |
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