DNA (deoxyribonucleic acid), the molecular basis of
heredity in nearly all life on earth, is most often
organized into linear structures within the cell
nucleus that are called chromosomes. Each
particular animal or plant species has a
characteristic, constant number of chromosomes.
Ploidy refers to the degree of repetition of this
basic chromosome number. While a majority of
organisms are diploid (possessing two complete
sets of chromosomes, or 2n), polyploids having
more than two complete sets are sometimes
observed, particularly in plants. In fact, triploids
(organisms having three chromosome sets, 3n) are
quite common in traditional plant agriculture. Most
bananas that are sold in commercial markets are
triploid, as are many ornamental flowers and trees.
Perhaps the most familiar triploid plant in
production today is the “seedless” watermelon.
Much less common than triploid plants, triploid
animals are sometimes utilized in production
situations, particularly those involving fish or
bivalve mollusks.