Dominance

Marijuana Horticulture

by Jorge Cervantes

Consider two true-breeding varieties; a white pistil variety and a variety showing only pink pistils. Both conditions are true-breeding and therefore homozygous; in each case sexual reproduction of each group separately leads to only pink pistil or white pistil plants respectively. An F1 hybrid, or the first generation cross of these two varieties, results in only white pistil plants; no pink pistils are seen regardless of how many F1 seeds are grown.

Upon sib mating of these F1 plants (crossing brothers t sisters, or mating F1 siblings), the resulting F2 generation produces 75% white pistil plants and 25% pink pistil plants. Notice the “disappearance” of the pink pistil plants in the F1 generation, and their subsequent “reappearance” in the F2 generation. In this case, white pistils are said to be dominant over pink pistils, and pink pistils are said to be recessive to white pistils.