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On March 31, 1968, then-incumbent U.S. president Lyndon B. Johnson made a surprise announcement during a televised address to the nation that began around 9 p.m., [1] declaring that he would not seek re–election for another term and was withdrawing from the 1968 United States presidential election.
A selectable marker is a gene introduced into cells, especially bacteria or cells in culture, which confers one or more traits suitable for artificial selection.They are a type of reporter gene used in laboratory microbiology, molecular biology, and genetic engineering to indicate the success of a transfection or transformation or other procedure meant to introduce foreign DNA into a cell.
McDonald–Kreitman test. The McDonald–Kreitman test[1] is a statistical test often used by evolutionary and population biologists to detect and measure the amount of adaptive evolution within a species by determining whether adaptive evolution has occurred, and the proportion of substitutions that resulted from positive selection (also known ...
In recombinant DNA technology, the ccdB gene is widely used as a positive selection marker (e.g. the Invitrogen's Zero Background and Gateway cloning vectors). [7] In August 2016, the CcdB positive selection technology falls completely within the public domain and is now fully free for personal or commercial use.
Tajima's D is a population genetic test statistic created by and named after the Japanese researcher Fumio Tajima. [1] Tajima's D is computed as the difference between two measures of genetic diversity: the mean number of pairwise differences and the number of segregating sites, each scaled so that they are expected to be the same in a neutrally evolving population of constant size.
Central tolerance. In immunology, central tolerance (also known as negative selection) is the process of eliminating any developing T or B lymphocytes that are autoreactive, i.e. reactive to the body itself. [1] Through elimination of autoreactive lymphocytes, tolerance ensures that the immune system does not attack self peptides. [2]
Marker assisted selection or marker aided selection (MAS) is an indirect selection process where a trait of interest is selected based on a marker (morphological, biochemical or DNA / RNA variation) linked to a trait of interest (e.g. productivity, disease resistance, abiotic stress tolerance, and quality), rather than on the trait itself. [1 ...
With positive selection, the cells expressing the antigen(s) of interest, which attached to the magnetic column, are washed out to a separate vessel, after removing the column from the magnetic field. This method is useful for isolation of a particular cell type, for instance CD4 lymphocytes.