Mitochondria have to be mentioned explicitly, since they were also recognized as containers of genetic material. These results were mainly gained by studies on yeasts, other fungi, protozoa and animal cells. During the sixties could it finally be verified that both plastids and mitochondria contain DNA that itself contains genetic information. A whole range of regularly structured green-white patterns follows Mendelian laws and is therefore determined by nuclear genes. Contrary to the phenomenons just mentioned do patterns occur that look as if numerous changes would take place during ontogenesis.
Green cells develop from a white cell line that again becomes green and so on.
These phenomenons were formerly thought to be caused by so-called 'fragile' genes. Today is it known that there exist indeed 'jumping' genes that act like switches on other genes. This is a situation that occurs always, when two different species cross. Sometimes does this pairing work and sometimes not. Plants with pale patches on the first leaves are rare.