Autopolyploid

Autopolyploid refers to an organism that possesses more than two complete sets of chromosomes, all derived from a single species. In autopolyploidy, chromosome sets originate by duplication within the same genome rather than by hybridization with different species.

Autopolyploidy can arise through several mechanisms. A common route is the formation of unreduced gametes (2n) during meiosis, which can fuse with a normal n gamete from the same species to form a triploid autopolyploid, or two 2n gametes fusing to produce a tetraploid (4n). Somatic chromosome doubling, or endoreduplication, can also generate autopolyploid individuals. These processes create individuals with multiple identical chromosome sets.

Meiosis in autopolyploids often involves complex chromosome pairing. Chromosomes may form multivalents (quadrivalents in tetraploids), leading to polysomic inheritance and a higher chance of unequal segregation, which can reduce fertility. Over time, genome stabilization and selection can restore fertility in some autopolyploid lineages, though fertility levels vary widely among species and lineages.

Autopolyploidy is an important mechanism in plant evolution and breeding. It can create instant reproductive isolation from the diploid ancestor and may confer advantages such as larger cell size, increased vigor, or novel traits. It is frequently exploited in crop improvement and plant breeding. A well-known example is the cultivated potato, Solanum tuberosum, which is autotetraploid.

In contrast to autopolyploidy, allopolyploidy involves combining chromosome sets from different species. Understanding the distinction between these forms helps clarify how polyploid species arise and behave genetically.