How can alleles show incomplete dominance?

When an allele isn't completely expressed over its paired allele for a specific trait, the result is an intermediate of the two allele, a third phenotype.

This is termed as incomplete dominance.

regulation of gene expression. gene expression can be regulated by various cellular processes with the aim to control the amount and nature of the expressed genes. these regulatory proteins bind to dna and send signals that indirectly control the rate of gene expression

explanation:

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: