There are three ways to determine the recessiveness of a gene, namely, self-crossing method, hybridization method and hypothesis method, as follows. 1. Self-crossing method: determine the dominance of traits by observing whether the progeny have traits segregating, cross the two parents with the same phenotype, if the traits different from the parents are recessive traits, and the same traits as the parents are dominant traits. 2. Hybridization method: only one trait appears in the progeny of the cross between the parents of different traits, the parent with this trait is a dominant purebred, F1 is a dominant heterozygote. 3. Assumption method: If the self and hybridization method can not determine the dominant and recessive, the assumption that the two parents of the same traits hybrid, if only one parent trait, is a dominant trait, if consistent with the fact that the assumption should be made that another identical parent hybrid, according to the assumptions of the conditions of the projected with the fact that it does not match. If it does not match, it means that the first hypothesis is valid. If it does, it is not possible to determine the dominant or recessive trait, and it can be confirmed by another experiment. It is recommended that if there is any discomfort, consult a doctor in time, do not be negligent, so as not to delay the disease.