Mendel studied 7 traits in pea plants. One of the monohybrid crosses he made was between plants with round seeds (R) and plants with wrinkled seeds (r). What was a conclusion that Mendel drew from the F2 generation of this cross?

Explanation:

Lets RR represent round seed

rr- wrinkled seed

RR × rr - Rr Rr Rr Rr. F1

Rr × Rr - RR Rr Rr rr F2

Mendel concluded from the F2 generation(second filial generation) that 75% (3/4) of the F2 carries the allele that is dominant for roundness and the plants shows the round seed phenotype

b. 25% (1/4) of the F2 plants shows the wrinkle seed phenotype

Two of the plants carried a recessive allele for wrinkle seed but the allele for rounder dominates over wrinkle seed.

Mendel concluded that each individual (plant) has a pair of factors (alleles), one for each trait (R and r) and that it separates (segregates) during the formation of the gametes. This conclusion is known as the segregation principle (First Mendels´ Low).

Explanation:

Mendel observed that the F1 expressed only one of the alternative variants (in this case, only rounded seeds appeared), while the other variant (wrinkle) disappeared. Mendel named "dominant" the expressed variant. Mendel allowed auto pollination and observed that in the second generation, F2, the other disappeared variant reappeared. Both alternative variants were present in the F2. Mendel named "recessive" the second alternative variant.

Mendel thought that hereditary traits determined by discrete factors were the possible explication for these phenotypes. These factors should have been present in the F1 in pairs. One of them came from one parental plant, and the other factor came from the other plant. These factors then separated again when sex cells were produced, giving two types of gametes, each with only one factor.

Mendel concluded that each individual (plant) has a pair of factors (alleles), one for each trait (R and r), and that the pair separates (segregates) during the formation of the gametes. This conclusion is known as the segregation principle (First Mendels´ Low).