In a study of black guinea pigs and white guinea pigs, 100 black animals were crossed with 100 white animals, and each cross was carried to an F₂ generation. In 94 of the crosses, all the F₁ offspring were black and an F₂ ratio of 3 black:1 white was obtained. In the other 6 cases, half of the F₁ animals were black and the other half were white. Why? Predict the results of crossing the black and white F₁ guinea pigs from the 6 exceptional cases.