Polyploidy

Polyploidy is the condition of having more than two complete sets of chromosomes. It can arise within a species or through hybridization between species.

Whole-genome duplication: The duplication of an organism’s entire nuclear genome. It directly produces additional complete chromosome sets.
Ploidy: The number of complete chromosome sets in a cell or organism. Polyploidy is a high-ploidy state, defined relative to diploidy.
Wheat: Cereal grasses cultivated for grain, including common bread wheat, an allohexaploid species. Bread wheat’s six chromosome sets arose through hybridization and genome doubling.
Polyploid speciation: The formation of a new species through the establishment of individuals with extra chromosome sets. A polyploid can become reproductively isolated from its diploid ancestors.
Gene balance hypothesis: The hypothesis that changes in relative gene copy numbers can disrupt molecular interactions and organismal fitness. It helps explain why some duplicated genes are retained together after polyploidy.
Nondisjunction: The failure of chromosomes or chromatids to separate properly during cell division. Errors in cell division can produce unreduced gametes that contribute to polyploidy.
Haploid: Having one complete set of chromosomes. A haploid set is the unit counted when describing polyploid chromosome number.
Cultivated potato: The domesticated tuber crop Solanum tuberosum, commonly cultivated as a tetraploid. Its four chromosome sets affect breeding and inheritance.
Reproductive isolation: The prevention of gene flow between populations by barriers to reproduction. Different chromosome numbers can make crosses produce sterile or low-fertility offspring.
Subfunctionalization: The partitioning of an ancestral gene’s functions between duplicated gene copies. It is one route by which duplicated genes persist after genome doubling.

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