(2)① From the information of gene composition in the table, it is not difficult to know that zucchini is diploid. As long as there is aD gene, the individual appears as a male plant.
② If a man is homozygous for aDaD, then his parents must both contain aD, which is obviously not in line with the actual situation. Therefore, there are no homozygous male plants in nature because there are no eggs with aD genotype.
③ A male plant crosses a female plant, and the offspring is hermaphrodite = 1: 1. It is not difficult to infer its genotype by combining the table information, so the genotype of the male plant is ADA+.
(4) Methods of verifying (genotype) plants: test crossing, selfing and pollen identification. For plants, the self-crossing method is simpler and more convenient, because existing varieties can be used and there is no need to look for recessive homozygotes; It can save the inconvenience of manual treatment such as emasculation, pollination and bagging, and make the results more reliable and accurate. Let hermaphroditic plants pollinate themselves and observe the sex type of their offspring. If their offspring are monoecious, then their parents' genotype is A+A+. If the ratio of bisexual plants to female plants is 3: 1, the genotype of parents is A+AD.
So the answer is:
(1) Not oriented? The order of base pairs is different.
(2)① Two? aD？ ② Eggs without aD genotype? ③aDa+
④ Let hermaphroditic plants pollinate themselves, and observe the sex type and proportion of offspring.
If the offspring are all hermaphroditic (monoecious), the parental genotype is a+a+;
If the bisexual plant: female plant in offspring is 3: 1, the genotype of parents is a+ad.