Clonal population

Ultimately a plasmid is defined by its mode of DNA repHcation. DNA repHcation is initiated at a single, characteristic sequence, termed the origin. The origin sequence determines the copy number of the plasmid relative to the host chromosome and the host enzymes that are involved in plasmid repHcation. Two different plasmids that contain the same origin sequence are termed incompatible. This term does not refer to the active exclusion of one plasmid by another from the ceU but rather to a stochastic process by which the two plasmids are partitioned differentially into progeny ceUs. A ceU which contains two plasmids of the same incompatibiHty group segregates two clonal populations, each of which has one of the two plasmids in it. 

Determining costs of secondary metabolites is inherentiy difficult as a result of the variable responses, multiple physiological roles of the metabolites, as well as the different types of costs involved in the production of secondary metabolites (production, transport, storage, maintenance) (Strauss et al. 2002). Emerging studies are now taking more of these variables into consideration. For example, work with clonal populations of D. pulchra has estimated costs of furanone production in relation to chemical defense and phenotype by investigations of reproductive... 

Medina JH, Viola H, Wolfman C, Marder M, Wasowski C, Calvo D, Paladini AC. (1997). Overview— flavonoids a new family of benzodiazepine receptor ligands. Neurochem Res. 22(4) 419-25. Menghini A, Mancini LA. (1988). TLC determination of flavonoid accumulation in clonal populations of Passiflora incarnata L. Pharmacol Res Commun. 20(suppl 5) 113-16. 

Coefficients of Variation and Phenotypic and Genotypic Variance, Heritability, and Genetic Gain Expected during Selection for 15 Traits in a Clonal Population... 

Initial transformation of a cell is believed, in most cases, to involve the co-operation of at least two oncogenes, or the inactivation of both copies of a tumor suppressor gene. Once the property of uncontrolled growth is established in a cell, a tumor develops. The initial transformation events originate in single cells, and, therefore, tumors are clonal. Other mutations that favor invasive and metastatic properties occur subsequently within members of the initial clonal population of tumor cells as they continue to divide. This process of selection gives rise to increasingly virulent populations of cancer cells (Micklos and Freyer, 1990 Liotta et al., 1991). 

Hobbs, M. M., Seiler, A., Achtman, M., and Cannon, J. G, Microevolution within a clonal population of pathogenic bacteria Recombination, gene duplication and horizontal genetic exchange in the opa gene family of Neisseria meningitidis. Mol. Microbiol. 12, 171-180 (1997). 

S-100 protein-positive cells may persist in the new clonal population cytokeratin-positive constituents are... 

For the integrating vector constructs we are using to express fluorescent proteins under control of the actin 15 promoter, there are two ways of modulating the expression level. First, to select an appropriate clone after transformation of the cells (for details see(6)). These vectors integrate randomly into the genome, and the level of expression depends on the site of integration. Second, even in a clonal population the expression varies from cell to cell. If green and red fluorescent proteins are expressed simultaneously, their levels fluctuate independently. Therefore, the experimentalist has to choose cells within a population that exhibit the optimal levels of expression (tee Note 4). 

Rapid multifluorescent TCRG Vy and Jy typing appbcation to T cell acute lymphoblastic leukemia and to the detection of minor clonal populations. Leukemia, 14, 1143-1152. 

The more it becomes clear that unicellular organisms can only be fully understood as members of a (clonal) population and of a biocenosis, the more it becomes apparent that in natural habitats cooperation between different organisms is as common as competition. Pheromones, taste, olfaction, and chemotaxis are central in social contacts of higher organisms, and similarly in symbiosis and related phenomena of microorganisms. Such cooperations are often facultative, i.e., the partners leave and have to find each other periodically. 

B. hermsii DAH is a wild-type non-clonal isolate that originated from blood of a human with relapsing fever (24). A clonal population of this isolate, designated DAH 2E7, was made by limiting dilution in liquid medium, and was infectious in RML mice by intraperitoneal injection (see Fig. 4). 

The presumptive mutant colonies to be isolated are first marked and the medium in the plate is removed. Individual colonies can then be loosened and the cells isolated using a capillary pipette. Cell colonies embedded in soft agar can similarly be picked. Between isolations, the pipette is cleaned and sterilized in boiling distilled water. The isolated mutant cells are inoculated into 35-mm plastic petri plates previously filled with complete growth medium without any additives. After a few days, when a sufficient cell number is reached, these clonal isolates of putative mutants are tested in appropriate media or growth conditions. Cytological examinations may also be made to determine the karyot)q)ic characteristics as well as the uniformity of the clonal populations. 

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