Mutation-Monitoring System

Before considering specific possibilities, I should like to list some of the criteria by which a mutation-monitoring system in man might be judged. It may be that no system will work. Or it may be that no system is worth the cost and that the effort might better be allocated elsewhere, e.g., to a more strenous attempt to detect mutagens in advance. 

Here are some of the questions to be asked of a mutation-monitoring system ... 

Crow (1971) has presented six criteria for a mutation-monitoring system, as follows ... 

Before considering possible monitoring systems, I should like to give a brief classification of the kinds of human effects that can reasonably be attributed to mutation and which could be expected to reflect an increase in the mutation rate. We can then ask which of these might best serve as the basis for a monitoring system, or whether it would be better to rely entirely on indirect evidence. 

The list that follows is roughly in order of the immediacy of the impact on the population. It is also roughly in order of the specificity of the mutational effect, and therefore the ease of detection in a monitoring system. On the other hand, it is likely that if the classification were arranged in order of the total impact on human welfare, the sequence should be reversed. 

Therefore, although recessive (or more correctly, nearly recessive) mutants probably make a very large impact on the population, they do it in a way that is exceedingly difficult to detect. If the effect is through homozygosity, it is likely to be far removed, both in time and space, from its origin by mutation. So this class of mutant would appear to be virtually useless in any phenotypic monitoring system. 

IV. SOME WAYS OF AMPLIFYING THE MUTATION-DETECTING POWER OF MONITORING SYSTEMS... 

I have been discussing mainly monitoring systems that depend on the detection of mutant phenotypes or on chemical and c)rtological indicators of mutation. It is clear from any numerical considerations that systems that depend on the monitoring of germinal mutations have to be done on a scale that may be too large to be feasible. 

A combination of efficient screening of a large number of somatic cells for chromosome breaks and an efficient way of measuring somatic point mutation rates—perhaps several systems involving different enzymes and with both forward and reverse mutations—seems to me to be the best nearfuture prospect for effective mutation monitoring. 

The technology for monitoring mutation in the human population is not yet sufficiently developed for wide application. However, there are systems that could be applied to selected populations, such as workers in a chemical factory. 

Five plant systems or types of study have been selected for coverage in this report plant cytogenetic analysis, chlorophyll mutations, the Tradescantia stamen hair test, the maize waxy locus system, and plant metabolic activation systems. Descriptions of other plant systems may be found in the proceedings of workshops on the use of higher plants as monitors for environmental mutagens94 and on the use of pollen systems to detect biologic activity of environmental pollutants.71... 

Bioassay is the quantitative method in which the endpoint is an observable effect on a biological system or an organism. The classical approach to microbial detection involves the use of differential metabolic assays (monitored colormetrically) to determine species type in the case of most bacteria, or the use of cell culture and electron microscopy to diagnose viruses and some bacteria that are intracellular parasites. Samples taken from the environment, such as soil and water, and most clinical samples must be cultured in order to obtain sufficient numbers of various cell types for reliable identification. The time required for microbial outgrowth is typically 4-48 hours (or two weeks for certain cases, such as Mycobacterium tuberculosis). Furthermore, bacterial culture suffers from an inherent drawback cells that are viable may not be culturable, because they possess unanticipated nutritional requirements as a result of genetic mutation. 

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