Question

How do mendel's experiments show that traits may be dominant or recessive

Answer 1

Mendel crossed two homozygous plants with a pair of contrasting traits, producing all hybrid plants showing the dominant trait morphologicaly.

A hybrid plant possessing factor, say Tt will be morphologicaly tall.

But... if two heterozygous plants were to be crossed. They would produce offsprings in the ratio 3:1. That one dwarf plant produced is homozygous. tt

This way Mendel showed through law of segregation, that genes separate and combine differently, either homozygous or heterozygous, resulting in the morphological expression of dominant or recessive character.