In the 1930's 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. mcclintock also hypothesized that segments of chromosomes could be broken or lost during the processes of mitosis and meiosis. 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 not yellow or blue corn kernals, but rather spotted kernals. barbara mcclintock's research provided important evidence for the presence of a) deletion. b) jumping genes. c) transcription. d) nondisjunction.