Spontaneous mutants

The repair status of the cell, that is, excision repair-deficient strains tend to have more spontaneous mutants than repair-proficient cells. 

Tests for mutation in Aspergillus nidulans are performed in hquid suspension. Conidia are exposed to the test substance both with and without metabohc activation and plated on selective medium to determine changes in colonial morphology or nutritional requirements. At the end of a suitable incubation period, mutant colonies are counted and compared to the number of spontaneous mutants in an untreated control culture. Simultaneous determination of survival... 

Heinz BA, Rueckert RR, Shepard DA, et al. Genetic and molecular analyses of spontaneous mutants of human rhinovirus 14 that are resistant to an antiviral compound. J Virol 1989 63(6) 2476-2485. 

There are two brown midrib mutants in pearl millet, one chemically induced (Chemey et al., 1988) and one spontaneous mutant (Degenhart et al., 1995). Analyses of the cell walls of these mutants bmr mutant indicated changes consistent with a reduction in COMT activity (Hartley et al., 1992 Degenhart et al., 1995 Lam et al., 1996), but the corresponding gene has not yet been cloned. 

During the studies on Alaaligenes faeoalis var. myxogenes 10C3, Harada and co-workers found that a spontaneous mutant,... 

Chronic Proliferative Dermatitis The chronic proliferative dermatitis mutant mouse is one of a number of mouse models proposed for psoriasis. This spontaneous mutant was recently shown to be caused by a mutation in the Sharpin gene (86). This mouse model was used to screen recombinant human cytokines in which recombinant interleukin 12 (IL-12) but not interleukin 11 (IL-11) effectively corrected the skin disease (28). 

One of these spontaneous mutants gave rise to the precious sticky rice of Thailand. The sticky rice lacks the starch amylose, which constitutes up to 30% of the total starch in nonsticky rice endosperm. The lack of amylose is due to a mutation in a gene called Waxy, which encodes an enzyme required for amylose synthesis (Sano 1984). Sticky rice is an important culinary and cultural component throughout East Asia and is used in festival foods and desserts. In upland regions of Southeast Asia, it is a staple food in many homes. Ten percent of the rice traded each year is sticky rice. 

Although definitive conclusions can only be made with sufficient clinical experience, a few studies with the spontaneous mutants have... 

Several spontaneous mutants of tomatoes have been Identified specifically as "ripening" mutants. The ripening Inhibitor (rlnl and non-rlpenlng (nor) mutations result In non-cllmacterlc fruits... 

Additional information <1, 7> (<7> spontaneous mutants with reduced enzyme activity [10] <1> deletion mutants in highly conserved regions, truncation mutants [13]) [10, 13]... 

Kaebemick, M. et al., A spontaneous mutant of microcystin biosynthesis genetic characterization and effect on Daphnia, Environ. Microbiol., 3, 669, 2001. 

Three important phenotypes can confer non-sensitivity to bacteriocins (i) immunity is genetically linked with bacteriocin production and exerts the strongest level of non-sensitivity, (ii) resistance can occur as the appearance of spontaneous mutants following selection on the bacteriocin and (iii) resistance conferred by a gene that is not genetically linked with bacteriocin production. These three categories of resistance are likely to be similar for any bacteriocin [21]. 

Two phenotypes, highly resistant [minimal inhibitory concentration (MIC) of 2000 xg mL j and moderately resistant strains (MIC 500 to 750 pg mL ) to streptomycin have been detected in the E. amylovora populations [64, 71, 72]. Spontaneous mutants with high level of resistance to streptomycin were isolated at a frequency of 4 of 10 bacteria and mutants with moderate resistance level were obtained at a frequency of 0.1 of 10 bacteria. 

Moniruzzaman, M. et al (1997) Isolation and molecular characterization of spontaneous mutants of ethanologenic Escherichia coli KOll containing the Klebsiella oxytoca casAB operon. Appl. Environ. Microbiol, 63, 4633. 

W-Methyltyramine was recently discovered by Kirkwood and Marion (4) in certain strains of barley. All attempts to isolate hordenine from these strains, which were regarded as spontaneous mutants, failed and it is presumed that they produce only iV-methyltyramine. The base has long been known as a product of the thermal or putrefactive decarboxylation of the natural W-methyltyrosinc, having been described at various times as surinamine, angeline, andirine, geoffroyine, and rhatanine (42-47). 

---