In the 1930s barbara mcclintock used corn to confirm thomas hunt morgan's theory of genetic crossing over. she traced the movement of a specific site on chromosome 9, in corn, during the formation of sex cells, or gametes. mcclintock noticed that the crossing over of this segment resulted in changes in physical traits of the corn. she also hypothesized that segments of chromosomes could be broken or lost during the processes of mitosis (cell division) and meiosis (gamete formation). mcclintock compared chromosome 9 in both yellow and blue kernalled corn. she observed that the gene for blue kernals could jump out of its normal location and reinsert itself somewhere else on the chromosome. this resulted in neither yellow nor blue corn kernals, but rather spotted kernals. the presence of spotted corn kernals rather than entirely blue or yellow was the result of