, Volume 2, Issue 4, pp 197-215

Genetics of polyploidy

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Conclusion

In general, then, genetic evidence from polyploids harmonizes surprisingly well with concepts based on the modern gene-chromosome law of heredity. This is true for both the individual hereditary characters and the organism as a whole. With the former, it is evident that character inheritance follows the particular gene distribution even when the cytological mechanism is disturbed by the addition of chromosomes.

The organism as a whole is also influenced by polyploidy but the relations of the parts are, nevertheless, maintained. The addition of one chromosome in a trisomic, for example, alters many individual characters and upsets the favorable balance of plus and minus factors established in the diploid by long continued selection. Nevertheless, the plant continues to function as a whole. This can mean only that there is a high degree of elasticity in an organism, affording a margin of safety for variable conditions. This may well explain the success of the mutation theory of evolution in giving new mutations time to become established and to become fitted into the germinal complex in which they arose. True polyploidy affords, in addition, extra gene loci as sources for new mutations. Such extra loci, as they mutate, must preserve a correlated function with their original sister loci and the polyploid condition would seem to afford time and protection for this process.

Paper No. 70, Department of Genetics, Iowa State College, Ames, Iowa.