As the zygote undergoes many rounds of mitosis to form an embryo and then a plant, the chloroplasts also divide and are distrusted randomly to daughter cells at each division.
Over the many cell divisions, some cells will have a pure set of normal chloroplasts (green patches) while others get a pure set of nonfunctional chloroplasts) white patches). Others yet will have a mix of normal and nonfunctional chloroplasts (mixed patches).
A branch that’s pure green will make egg cells with green chloroplasts that give rise to pure green offspring. Similarly, a branch that’s pure white will make egg cells that contain only white chloroplasts and will give rise to pure white offspring.
If a branch is variegated, the cell types may give rise to egg cells that lead to green, white, or variegated offspring in unpredictable ratios.
