The Genetics of Resistance

Lewis M.J. (1989) The genetics of resistance. In Antimicrobial Chemotherapy (ed. D. Greenwood), 2nd edn, pp. 146-152. Oxford Oxford University Press. 

The resistance to ozone-induced tipburn in onions mentioned earlier is being incorporated into commercial onion varieties primarily for the Midwest at the University of Wisconsin (12). In a program at the University of Tennessee, dark green vigorous trees have been selected in stands of eastern white pine in which most trees have died because of sensitivity to ozone, S02, and automobile exhaust constituents. Crosses have been made to determine the genetics of resistance, and a formal breeding orchard of resistant trees has been established (13). 

S- and R-insects are killed by the pesticide. If mahng is random, inihally rare homozygous R-individuals are likely to mate with the more abundant homozygous suscephble insects that have not been exposed to the insech-cide. In most cases, where the genetics of resistance have been studied, the resistance alleles are recessive or semidominant. 

Taken together, the genetic barrier cannot be simply defined by the sum of resistance mutations, but also the genetic background of the virus, the variation in the viral population, interaction of mutations, and their impact on viral replication play a role. 

Mergeay, M., Towards an understanding of the genetics of bacterial metal resistance, Trends Biotechnol, 9 (1), 17-24, 1991. 

Table 10. Genes affected by point mutations or other genetic events leading to antibiotic resistance in II. pylori and the frequency of resistance (from Megraud and Lamouliatte [166])...

While the mechanism of resistance to various synthetic pyrethroids in flies has been elucidated in terms of physiology, biochemistry, and genetics, it seems that the resistance mechanism is mostly common to mosquitoes. 

When simple substances, even those that are intimately associated with living processes, are tested upon organisms, the results may be highly variable depending on the genetics of the organism tested. Thus, there are strains of Drosophila which are sensitive and resistant, respectively, to carbon dioxide. Some can stand hours of contact with pure carbon dioxide without permanent injury, while others either do not recover from the narcosis or, if they do, their movements... 

Krus S, Zaleska-Rutczynska Z. 1969. Morphological counterparts of the genetically determined resistance of mice to chloroform poisoning. Experientia 26 101-102. 

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