When Mendel crossed tall and dwarf plants, the F2 generation showed a 3:1 ratio of tall to short plants. From this result, he concluded:
I. Law of dominance
II. Law of independent assortment
III. Incomplete dominance
IV. Law of segregation

Choose the correct option.

 I and IV

The correct answer is Option (3) -  I and IV

The correct answer is based on Mendel's findings during his experiments on pea plants. In the F2 generation, he observed a 3:1 ratio of tall to short plants when crossing a tall (dominant) plant with a dwarf (recessive) plant. This led to the following conclusions:

1. Law of Dominance: In a cross between two contrasting traits, one trait (dominant) will mask the expression of the other (recessive).
2. Law of Segregation: During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene. This explains the 3:1 ratio in the F2 generation, where both dominant and recessive traits appear.

The Law of Independent Assortment deals with the inheritance of two or more traits and does not apply to the 3:1 ratio observed here, while incomplete dominance (where traits blend rather than one dominating) is not relevant to this situation. Therefore, only the law of dominance and the law of segregation apply to this scenario.