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. Which of the following explains why there were such different results for a cross of a black and a white guinea pig? The trait is determined by two loci; all of the black individuals were heterozygous at both loci. The trait is determined by a single locus; some black individuals were homozygous and others were heterozygous The trait is determined by two loci; some black individuals were homozygous at both loci and others were heterozygous'at both loci. The trait is determined by a single locus; all of the black Individuals were heterozygous.