Final answer:
Mendel explained the reappearance of the wrinkled pea trait in the F2 generation by introducing the concept of dominant and recessive traits. In this case, the round pea trait was dominant and the wrinkled pea trait was recessive. So, in the F1 generation, all plants had round peas due to inheriting a dominant round pea trait, while in the F2 generation, when the F1 plants self-fertilized, some F2 plants received two recessive wrinkled pea traits and exhibited the wrinkled pea phenotype.
Step-by-step explanation:
Mendel observed that when he performed his experiments, only one trait appeared in the F1 generation (in this case, round peas), and the other trait (wrinkled peas) seemed to have disappeared. However, when Mendel allowed the plants of the F1 generation to self-fertilize, the wrinkled peas reappeared in the F2 generation. Mendel explained this phenomenon by proposing the existence of dominant and recessive traits. In this case, the round pea trait was dominant, while the wrinkled pea trait was recessive. This meant that in the F1 generation, all the plants had round peas because they inherited one dominant round pea trait from one parent. When these F1 plants self-fertilized, some of the F2 plants received two recessive wrinkled pea traits and exhibited the wrinkled pea phenotype.