Question

How do Mendel's experiments show that the
(a) Traits may be dominant or recessive
(b) Traits are inherited independently

Answer 1

(a) Monohybrid cross between two pure breeding varieties always obtained hybrid progeny exhibiting one parental trait while the other trait was never expressed in $F_1$ generation. It suggested that two alleles of a gene can be either dominant or recessive and presence of the dominant allele in $F_1$ hybrids masks the expression of recessive one.

(b) A dihybrid cross between two pure breeding varieties obtains dihybrid progeny exhibiting the only dominant trait. However, selfing of $F_1$ hybrids obtains both parental and new combinations of traits in 9:3:3:1 ratio in $F_2$ generation suggesting an independent assortment of characters.