In eukaryotic organisms, chromosomes come in sets. The somatic cells, called soma, usually have a diploid chromosome number, which in scientific notation is abbreviated as 2N. The diploid state contains two sets of chromosomes, one set of which has been contributed by each parent. A single set of chromosomes composes the haploid chromosome number, which is abbreviated as N. The haploid set is found in reproductive cells or gametes (also called the germplasm). In humans the diploid number is 46, and is represented as 2N = 46. Human sperm or eggs, however, have a haploid number of 23, which is represented as N = 23. In some circumstances, however, an organism can have more than two chromosomal sets. This occurrence is called polyploidy.

One cause of polyploidy is polyspermy. If two sperm fertilize an egg, the resulting zygote or fertilized egg will have three sets of chromosomes, and thus have a triploid number (3N...