Marbling in plants as seen in the images on the right is due to a transposon. It's a small piece of DNA the that can jump into, and out of, other strands of DNA. If it jumps into a strand that makes chlorophyl or pigment, it prevents that gene from being expressed. If a gene is not expressed the protein it makes is not expressed, and thus a lack of color in the leaves. As the transposon can also jump out, the marbling is unstable and can be lost over time. This instability is what makes each leaf unique in a marbled plant. Depending on whether they are in or out of the genome, they may or may not be inherited by sexual breeding, they would be inherited by division.