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A chemical is considered positive for Ames test if it causes mutations increasing the observed reversion rate and negative if presents similar to the control group. There is a normal, but small, number of revertant colonies expected when an auxotrophic bacteria is plated on a media without the metabolite it needs because it could mutate back to ...
Point mutations are modifications of single base pairs of DNA or other small base pairs within a gene. A point mutation can be reversed by another point mutation, in which the nucleotide is changed back to its original state (true reversion) or by second-site reversion (a complementary mutation elsewhere that results in regained gene ...
The Luria–Delbrück experiment (1943) (also called the Fluctuation Test) demonstrated that in bacteria, genetic mutations arise in the absence of selective pressure rather than being a response to it. Thus, it concluded Darwin 's theory of natural selection acting on random mutations applies to bacteria as well as to more complex organisms.
Bacterial recombination. Bacterial recombination is a type of genetic recombination in bacteria characterized by DNA transfer from one organism called donor to another organism as recipient. This process occurs in three main ways: Transformation, the uptake of exogenous DNA from the surrounding environment.
Ames test procedure. The Ames test is a widely employed method that uses bacteria to test whether a given chemical can cause mutations in the DNA of the test organism. More formally, it is a biological assay to assess the mutagenic potential of chemical compounds. [1] A positive test indicates that the chemical is mutagenic and therefore may ...
A suppressor mutation is a second mutation that alleviates or reverts the phenotypic effects of an already existing mutation in a process defined synthetic rescue. Genetic suppression therefore restores the phenotype seen prior to the original background mutation. [1] Suppressor mutations are useful for identifying new genetic sites which ...
In this image, a gene from one bacterial cell is moved to another bacterial cell. This process of the second bacterial cell taking up new genetic material is called transformation. In molecular biology and genetics, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic ...
Bacterial growth. Growth is shown as L = log (numbers) where numbers is the number of colony forming units per ml, versus T (time.) Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providing no mutation event occurs, the resulting daughter cells are genetically identical to the original ...