Autotetraploid

Autotetraploid refers to an organism or cell that contains four complete sets of chromosomes (4n), all derived from duplication of a single genome. In autotetraploids the four chromosome sets are homologous to each other, unlike in allopolyploids, where the extra sets derive from different species. Autotetraploidy can arise by genome doubling in a diploid organism or by the fusion of two unreduced (2n) gametes during fertilization.

Formation: Autotetraploids arise when a diploid (2n) cell doubles its chromosome number (somatic doubling, possibly via nondisjunction or endoreduplication), or when two unreduced (2n) gametes fuse at fertilization to form a 4n zygote.

Meiosis and fertility: Meiosis in autotetraploids features multivalent chromosome pairing and can yield unbalanced gametes, leading to reduced fertility, especially in early generations. Over time, selection and chromosomal rearrangements can stabilize meiosis and restore some fertility. Autotetraploids often have larger cells and organs, sometimes with boosted vigor, which can be advantageous in agriculture and horticulture.

Applications and examples: Potatoes (Solanum tuberosum) are a common cultivated autotetraploid; other plant lineages show natural autopolyploidy, such as Arabidopsis arenosa. Autotetraploids are used in breeding to fix heterozygosity and create desired traits, though fertility and seed production may be limited. Detection relies on chromosome counting, flow cytometry of DNA content, or genomic analyses.