Mendel proposed that the factor controlling any character is discrete and independent. This proposition was based on which of the following observations?

Characters are controlled by discrete units called factors. This was proposed by Mendel as only one of the parental characters in a monohybrid cross in the F1 and the expression of both in the F2. The alleles do not show any blending and that both the characters are recovered as such in the F2 generation though one of these is not seen at the F1 stage.