Most eukaryotes have genomes that exhibit high levels of gene redundancy, much of which appears to have arisen from one or more cycles of genome doubling. Polyploidy has been particularly prominent during flowering plant evolution, yielding duplicated genes (homoeologs) whose expression may be retained or lost either as an immediate consequence of polyploidization or on an evolutionary timescale.

There are four possible expression outcomes: equal expression (a gene derived from the parental "A" genome in the polyploid is expressed at the same level as its homoeolog derived from parental genome "D"), biased expression (one homoeolog is more abundantly expressed than its corresponding homoeolog), gene silencing (one homoeolog is expressed while the other is not), and novel expression (expression in the polyploid that was not present in the parents).