A heterozygous plant, for a pair of alleles B/b (B encodes yellow and b encodes bronze) was selfed. In the progeny 280 yellow and 120 bronze plants occur. The hypothesis is given by:
In a cross between heterozygous plants, the progeny in the F1 generation should be of the ration 3:1. But, the actual ratio gives more approximately a ratio of 2:1. This proves that one of the dominant allele in a homozygous condition is lethal (B/B).
Hence, these results support the fact that the plant involved in a cross is a heterozygous.