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| Cation |
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A positively charged ion.
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| cDNA |
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DNA synthesized from an RNA template using reverse transcriptase.
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| cDNA library |
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A library composed of complementary copies of cellular mRNAs. (See Library.)
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| Cellular oncogene (proto- |
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A normal gene that when mutated or improperly expressed contributes to the development of cancer. (See Oncogene.)
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| Centers of origin |
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Usually the location in the world where the oldest cultivation of a particular crop has been identified.
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| Central dogma |
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Francis Crick's seminal concept that in nature genetic information generally flows from DNA to RNA to protein.
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| Centrifugation |
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Separating molecules by size or density using centrifugal forces generated by a spinning rotor. G forces of several hundred thousand times gravity are generated in ultracentrifugation. (See Density gradient centrifugation.)
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| Centromere |
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The central portion of the chromosome to which the spindle fibers attach during mitotic and meiotic division.
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| Chemotherapy |
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A treatment for cancers that involves ad- ministering chemicals toxic to malignant cells.
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| Chloramphenicol |
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An antibiotic that interferes with protein synthesis.
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| Chromatid |
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Each of the two daughter strands of a duplicated chromosome joined at the centromere during mitosis and meiosis.
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| Chromosome |
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A single DNA molecule, a tightly coiled strant of DNA, condensed into a compact structure in vivo by complexing with accessory histones or histone-like proteins. Chromosomes exist in pairs in higher eukaryotes. (See Chromosome walking.)
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| Chromosome walking |
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Working from a flanking DNA marker, overlapping clones are successively identified that span a chromosomal region of interest. (See Chromosome.)
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| Cistron |
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A DNA sequence that codes for a specific polypeptide; a gene. See DNA, Gene.
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| Clone |
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An exact genetic replica of a specific gene or an entire organism. See Cloning.
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| Cloning |
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The mitotic division of a progenitor cell to give rise to a population of identical daughter cells or clones. (See Directional cloning, Megabase cloning, Molecular cloning, Subcloning.)
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| Coat protein (capsid). |
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The coating of a protein that enclosed the nucleic acid core of a virus.
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| Codon |
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A group of three nucleotides that specifies addition of one of the 20 amino acids during translation of an mRNA into a polypeptide. Strings of codons form genes and strings of genes form chromosomes. (See Initiation codon, Termination codon.)
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| Coenzyme (cofactor). |
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An organic molecule, such as a vitamin, that binds to an enzyme and is required for its catalytic activity.
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| Colony |
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A group of identical cells (clones) derived from a single progenitor cell.
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| Commensalism |
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The close association of two or more dissimilar organisms where the association is advantageous to one and doesn't affect the other(s). See Parasitism, Symbiosis.
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| Competency |
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An ephemeral state, induced by treatment with cold cations, during which bacterial cells are capable of uptaking foreign DNA.
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| Complementary DNA or RNA |
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The matching strand of a DNA or RNA molecule to which its bases pair. (See DNA, RNA.)
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| Complementary nucleotides |
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Members of the pairs adenine-thymine, adenine-uracil, and guaninecytosine that have the ability to hydrogen bond to one another. (See nucleotide.)
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| Concatemer |
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A DNA segment composed of repeated sequences linked end to end.
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| Conjugation |
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The joining of two bacteria cells when genetic material is transferred from one bacterium to another.
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| Constitutive promoter |
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An unregulated promoter that allows for continual transcription of its associated gene. (See Promoter.)
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| Contiguous (contig) map |
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The alignment of sequence data from large, adjacent regions of the genome to produce a continuous nucleotide sequence across a chromosomal region. (See Mapping.)
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| Cross-hybridization |
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The hydrogen bonding of a single- stranded DNA sequence that is partially but not entirely complementary to a singlestranded substrate. Often, this involves hybridizing a DNA probe for a specific DNA sequence to the homologous sequences of different species.
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| Crossing-over |
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The exchange of DNA sequences between chromatids of homologous chromosomes during meiosis.
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| Cross-pollination |
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Fertilization of a plant from a plant with a different genetic makeup.
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| Culture |
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A particular kind of organism growing in a laboratory medium.
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| Cyclic AMP (cyclic adenos |
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A second messenger that regulates many intracellular reactions by transducing signals from extracellular growth factors to cellular metabolic pathways.
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| Cytogenetics |
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Study that relates the appearance and behavior of chromosomes to genetic phenomenon.
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| Dalton |
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A unit of measurement equal to the mass of a hydrogen atom, 1.67 x 10E-24 gram/L (Avogadro's number).
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| Death phase |
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The final growth phase, during which nutrients have been depleted and cell number decreases. (See Growth phase).
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| Denature |
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To induce structural alterations that disrupt the biological activity of a molecule. Often refers to breaking hydrogen bonds between base pairs in double-stranded nucleic acid molecules to produce in single-stranded polynucleotides or altering the secondary and tertiary structure of a protein, destroying its activity.
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| Density gradient centrifu |
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High-speed centrifugation in which molecules "float" at a point where their density equals that in a gradient of cesium chloride or sucrose. (See Centrifugation.)
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| Deoxyribonucleic acid |
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See DNA, nuclease.
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| Diabetes |
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A disease associated with the absence or reduced levels of insulin, a hormone essential for the transport of glucose to cells.
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| Dideoxynucleotide (didN). |
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A deoxynucleotide that lacks a 3' hydroxyl group, and is thus unable to form a 3'-5' phosphodiester bond necessary for chain elongation. Dideoxynucleotides are used in DNA sequencing and the treatment of viral diseases. (See Nucleotide.)
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| didN |
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See Dideoxynucleotide.
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| Digest |
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To cut DNA molecules with one or more restriction endonucleases.
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| Diploid cell |
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A cell which contains two copies of each chromosome. See Haploid cell.
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| Directional cloning |
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DNA insert and vector molecules are digested with two different restriction enzymes to create noncomplementary sticky ends at either end of each restriction fragment. This allows the insert to be ligated to the vector in a specific orientation and prevents the vector from recircularizing. (See Cloning.)
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| DNA (Deoxyribonucleic aci |
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An organic acid and polymer composed of four nitrogenous bases--adenine, thymine, cytosine, and guanine linked via intervening units of phosphate and the pentose sugar deoxyribose. DNA is the genetic material of most organisms and usually exists as a double-stranded molecule in which two antiparallel strands are held together by hydrogen bonds between adeninethymine and cytosine-guanine. (See b-DNA, cDNA, Complementary DNA or RNA, DNA polymorphism, DNA sequencing, Double-stranded complementary DNA, Duplex DNA, Z-DNA.)
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| DNA diagnosis |
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The use of DNA polymorphisms to detect the presence of a disease gene.
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| DNA fingerprint |
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The unique pattern of DNA fragments identified by Southern hybridization (using a probe that binds to a polymorphic region of DNA) or by polymerase chain reaction (using primers flanking the polymorphic region).
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