tripploids

Triploids are organisms with three complete sets of chromosomes, designated 3n. In most species, having three chromosome sets disrupts meiosis because homologous chromosomes fail to pair evenly, producing unbalanced gametes. As a result, triploids are often sterile and cannot produce normal offspring, though some can reproduce asexually or vegetatively. Triploidy occurs naturally in some plants and animals and is also deliberately induced in agriculture and aquaculture to produce seedless or sterile stock.

Triploids form in several ways. They can arise when a haploid gamete (n) from one parent fuses with a diploid or unreduced gamete (2n) from another parent, giving 3n offspring. They can also originate from fertilization of an unreduced 2n gamete by a normal 1n gamete, or from interspecific hybridization between species with different chromosome numbers. Artificial induction with spindle inhibitors such as colchicine or through endoreduplication can create 3n zygotes.

In plants, triploidy is exploited to produce seedless varieties and to combine desirable traits from different genomes. In agriculture, seedless watermelons are often triploids derived from crossing diploid and tetraploid parents, and many cultivated bananas are triploid, contributing to their edible, seedless state. In animals, triploidy is usually lethal in mammals; most triploid embryos fail to develop. Some fish and amphibians can be viable triploids and are used in research or aquaculture because they are sterile, reducing crossbreeding with wild populations.

Detection and study rely on chromosome counting (karyotyping) or measuring DNA content (flow cytometry) to determine ploidy level.