Mendel deduced that each parent in a monohybrid cross contributes:

1. The F2 ratios could not be explained by blending or by whole-genome inheritance. 2. On the basis of his results in F1 and F2 generations, Mendel postulated that each parent in the monohybrid cross contributed one of two paired unit factors to each offspring. 3. Every possible combination of unit factors was equally likely. 4. Those unit factors are what we now call alleles. 5. If each parent contributed both factors the offspring would be tetraploid, which they are not. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 12 'Mendel's Experiments and Heredity', sections 12.1-12.3_