How do Mendel’s experiments show that traits may be dominant or recessive
When Mendel crossed a pure tall variety of pea with the dwarf pea plant, all its progeny were tall. Presence of only one trait here indicates that when plants with two contrasting features are cross-pollinated, one variety expresses itself while the latter variety remains dormant. We call this observation as the law of dominance.
Mendel again cross-pollinated the f1 generation. Here the hidden trait reappeared in the F2 generation. From this Mendel concluded that some factors (now called gene) transfer itself during pollination. These factors exist in pair; one factor is dominant while the other is recessive.