One of the most important processes in the evolution of flowering plants is doubling of the chromosomes, or polyploidy. At least 50% of all plants and nearly all of the major crop plants of the world are polyploid derivatives from diploid, wild stocks. Knowledge of how the process of polyploidization works is poor, as is understanding of the consequences with respect to the organization and function of genes along the chromosomes. Dr. Jonathan Wendel of Iowa State University is examining the problem of polyploidy using the cultivated cotton plant and its wild relatives as a model system. Using modern molecular methods, detailed genetic maps will be constructed of the chromosomes of both polyploid and diploid species. The primary experiments involve isolating several hundred pieces of DNA by restriction-site digests and ascertaining their relative locations on individual chromosomes. Then, comparisons of gene arrangements among species will reveal the extent to which particular pieces of DNA have changed position on chromosomes and whether the DNA has undergone increase or decrease in copy number. Such changes in DNA have been hypothesized to have regulatory effects on the form and function of the organism. Dr. Wendel's research will lay the basis for a genetic explanation of morphological differences among plant species.
