Conditional mutant

Baron U, Schappinger D, Helbl Vet al (1999) Generation of conditional mutants in higher eukaryotes by switching between the expression of two genes. Proc Natl Acad Sci USA 96 1013-1018... 

The third method uses genetic mutation as the primary tool. This method requires the isolation of conditional mutants, that is, mutants that behave normally under one set of conditions but abnormally under another. Most commonly, temperature-sensitive DNA replication mutants are used. Such mutants have been isolated in E. coli, and they grow normally at a low (permissive) temperature (33°C) but poorly or not at all at a high (nonpermissive) temperature (41°C). Preliminary analysis of the temperature-sensitive step provides clues to the stage of replication affected. For... 

The enzyme that converts CDP-DAG and //no-inositol to PI belongs to the CDP-alcohol phosphatidyltransferase class-I family. In yeast, the enzyme is located in the outer mitochondrial membranes and microsomes (Nikawa and Yamashita, 1997). In M. tuberculosis, thepgsA gene was identified as encoding a PI synthase enzyme by construction of a conditional mutant. The strain would not grow under non-permissive conditions. There was also a noted loss of cell viability when PI and PI dimannoside dropped to 30% and 50% of what occurs in wild type cells. Therefore PI and the machinery to make it are essential for survival of mycobacteria (Jackson et al., 2000). 

Hallonet, M., Kaestner, K.H., Martin-Parras, L., Sasaki, H., Betz, U.A., Ang, S.L. 2002. Maintenance of the specification of the anterior definitive endoderm and forebrain depends on the axial mesendoderm a study using HNF3beta/Foxa2 conditional mutants. Dev. Biol. 1, 20-33. 

Boitz JM, Ullman B. A conditional mutant deficient in hypoxanthine juanine phosphoribosyliransfeiase and xanthine phosphoribosylttansfetase validates the purine salvage pathway of Leishmania donovani. J Biol Chem 2006 281(23) 16084-9. 

Puhna MV, Sahr KE, Nowotschin S, Baron MH, Hadjantonakis AK. 2014. A conditional mutant allele for analysis of Mixll function in the mouse. Genesis 52(5) 417-423. 

Calcium is a Competitive Inhibitor of the Activation of Oxygen Evolution by Manganese in Conditional Mutants of Scenedesmus obliquus 929... 

Second, Tazima tested the lethality of these mutations in homozygous condition. Mutants for testing were obtained by irradiating several stages of germ cells in both sexes. Among 116 tested, 37 were viable and 79 were accompanied by embryonic lethality. 

Fig. 20, Defective phenotypes of conditional mutants of T4D under restrictive conditions. Characterized genes are represented by shaded areas illustrating relative locations, and, if known, approximate map lengths. The enclosed symbols indicate defective phenotypes as follows DNA NEG. noDNA synthesis DNA ARREST DNA synthesis arrested after a short time DNA DELAY DNA synthesis commences after some delay MAT DEF. maturation defective, DNA synthesis is normal but late functions are not expressed a hexagtm indicates that free heads are produced, an inverted T, that free tails are produced TAIL FIBER fiberless particles produced gene 9 mutants produce inactive particles with contracted sheaths g e 11 and 12 mutants produce ftagile particles which dissociate to free heads and free tails. (Edgar and Wood, 1966).

The elucidation of the control mechanism of membrane protein synthesis could be rendered easier if appropriate conditional mutants, such as temperature-sensitive mutants for membrane protein synthesis or regulatory mutants, would be available. Such mutants could prove to be priceless tools if they could be obtained for specific proteins, such as the different components of the L protein group or the hypothetic repressor for the synthesis of these proteins. At the time of this writing, temperature-sensitive mutants for membrane proteins required for photosystem II activity have been obtained and are under investigation (P. Benoun, personal communication). Temperature-sensitive mutants of C. reinhardi for all the cyto-... 

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