How many true-breeding pea plant varieties did Mendel select as pairs,which were similar except in one character with contrasting traits?

$F_1$ generation Mendel pollinated a pure-breeding tall plant with a pure-breeding dwarf plant. But for getting the $F_2$ generation,he simply self-pollinated the tall $F_1$ plants. Why?

From a single ear of corn,a farmer planted $200$ kernels which produced $140$ tall and $40$ dwarf plants. The genotypes of these offspring are most likely:

Differentiate between Dominance and Recessive traits.

In Mendelism,linkage was not observed due to

If Mendel had studied $7$ pairs of traits in a plant with $12$ chromosomes instead of $14$,then: