Co - dominance : When the relationship between a pair of alleles in an organism is not the same as dominant and recessive, but both affect El hybrids together, then such a situation is called co - dominance and such alleles are called co - dominant alleles.
Incomeplete dominance : Mendel's experiment selected seven pairs of traits, one allele was completely dominant and the other recessive, but there are some instances where Mendel's law of absolute dominance does not apply. In contrasting pairs of traits, one trait shows an incomplete effect on another trait. This is called incomplete effectiveness.