When Gregor Mendel conducted his pea plant experiments, he began by crossing two true-breeding plants with different traits. True-breeding plants are those that, when self-pollinated, produce offspring identical to the parents. These initial plants represent the parental generation.
When Mendel crossed these plants, he observed the following in the next generations:
1. F_1 Generation (First Filial Generation): All of the offspring in the F_1 generation exhibited only one of the two parental traits. For instance, if he crossed a plant with purple flowers with a plant with white flowers, all F_1 offspring had purple flowers. This indicated that one trait was dominant over the other.
2. F_2 Generation (Second Filial Generation): Mendel then allowed the F_1 plants to self-pollinate. In the resulting F_2 generation, he observed a reappearance of the recessive trait. Approximately 75% of the F_2 plants showed the dominant trait, while 25% showed the recessive trait, leading to the classic 3:1 ratio Mendel is known for.
Based on these observations, Mendel concluded that traits are inherited as discrete units (now known as genes) and do not blend. Some traits, which he referred to as dominant, could mask the presence of recessive traits in the F_1 generation.
Therefore, the correct observation that Mendel made is:
B. Some traits that were not visible in the [tex]$F_1$[/tex] generation reappeared in the [tex]$F_2$[/tex] generation.
