Genetic changes

There is a small probability of a genetic change occurring each time a cell divides. Therefore, selection of natural variants may result in increased yields but it is not possible to rely on such improvement, and techniques must be employed to increase the chances of improving the culture. 

Medicago sativa Not fully determined. Lethal genetic changes after long-term culture (3)... 

This suggests that it may be possible to manipulate the rhizosphere flora through genetic changes in the host plant. Of particular interest is whether different varieties, by exuding different compounds, can influence the rhizosphere flora in a way that would benefit the plant. 

Tumor cells may become resistant when genetic changes occur during cell proliferation. Resistant cancer cells with the mdr-1 gene may possess a membrane-associated protein, p-glycoprotein, that facilitates efflux of chemotherapy agents out of the cells. Numerous attempts at blocking this efflux pump have been unsuccessful. 

The ability to detect small genetic changes becomes more difficult as mass increases. There is further an upper mass range where analysis is impractical. For low-resolution instruments this limit is around a 100 mer. Thus the mass has to be minimized or a high-resolution instrument employed. Alternatively, the smaller the piece of DNA analyzed, the more it chemically resembles a primer or nucleotide monomer thus separation of the two during cleanup is difficult to do. If the primers and nucleotides are not removed, they can provide a massive background on MS analysis or inhibit ionization of the PCR product by preferential ionization. Thus for practical reasons it is extremely difficult to employ a PCR product below a 40 to 50mer for direct ESI MS or ESI MS-MS analysis. 

A mechanism for genetic change, so that a newly created member of the population need not be an exact copy of a previous member. 

This reflects the observation that genetic change among living species is based on the current chromosome (hence, the mean of zero) and that small changes to it are more likely than large ones (hence, the dependence of the size of the change on a normal distribution with a limited standard deviation). The solution, which corresponds to the new set of parameters, is then calculated. 

Transpositions several viruses are known which act essentially as transposons and transposition events involving viruses can lead to their genetic change. 

Towards the end of each chapter, we have put a section on genetic changes in order to relate the account of evolution we are giving to that of more traditional... 

The capacity of some agent or chemical substance to induce genetic changes resulting from chromosomal alterations, which changes may be transmitted from parent to offspring. 

Sequential mutations within colonic epithelium result in cellular replication or enhanced invasiveness. Genetic changes include mutational activation of oncogenes and inactivation of tumor suppressor genes. 

The activity of p38/SAPK is central to the genetic changes that occur in response to cytokine activated pro-inflammatory signaling in astrocytes and microglia. p38/SAPK... 

Mutations may also occur in a single cell within an early embryo. As all the cells divide during growth and development, the individual will have some cells with the mutation and some cells without the genetic change. This situation is called mosaicism. 

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