Polyploid cells are cells containing multiple copies of their chromosomes. This often occurs in plants: wheat, for example, after millennia of hybridization and modification by humans, has strains that are diploid (with two sets of chromosomes), tetraploid (with four sets of chromosomes) with the common name of macaroni wheat, and hexaploid (with six sets of chromsomes) with the common name of bread wheat.

Polyploidy can be induced in cell culture by some chemicals: the best known is Colchicine, which causes chromosome doubling.

See also : ploidy -- biology -- genetics