Final answer:
McClintock's work on maize kernel color variation revealed non-Mendelian inheritance patterns due to mobile genetic elements known as the Ac/Ds system, causing unstable genes and resulting in variegated colors on corn kernels.
Step-by-step explanation:
The work of Creighton and McClintock focused on the genetics of maize kernel color variation, particularly looking at the role of the Ac/Ds system in mosaicism. These studies are a classic example of inheritance patterns that don’t strictly follow Mendelian genetics due to the presence of mobile genetic elements. In their experiments, McClintock observed that while the expected outcome from a genetic cross was colorless (yellow) aleurone cells stemming from the dominant C' allele, many kernels displayed variegated patterns with dark spots or streaks, indicating that the Ds (Dissociator) gene was causing chromosomal changes in some of the cells.
This non-Mendelian inheritance suggested that some genes could be unstable, leading to changes in the phenotype of somatic cells within an organism, resulting in mosaic patterns of colored and colorless areas on maize kernels. The discovery of this genetic behavior provided insight into mobile genetic elements, laying the groundwork for future studies of genetic regulation and mutation.