allopolüploidses

Allopolyploidy is a condition in which an organism has more than two sets of chromosomes, and these chromosome sets originate from different species. This is in contrast to autopolyploidy, where the extra chromosome sets come from the same species. Allopolyploidy typically arises through hybridization between two different species, followed by a doubling of the chromosome number in the hybrid offspring. This doubling event restores fertility to the hybrid, which would otherwise be sterile due to problems with chromosome pairing during meiosis.

The process often involves the initial formation of a hybrid that has an uneven number of chromosomes from each parent species. For example, if species A has n chromosomes and species B has m chromosomes, the hybrid will have n+m chromosomes. If n and m are different, homologous chromosomes from the two parent species will not be able to pair up effectively during meiosis, leading to aneuploid gametes and sterility. However, if the chromosome number doubles in the hybrid, resulting in 2n+2m chromosomes, then there will be two complete sets of chromosomes from species A and two complete sets from species B. This allows for proper pairing of homologous chromosomes (one set from species A with its counterpart from species A, and similarly for species B), leading to the production of viable gametes and fertile offspring.

Allopolyploidy is a significant mechanism in plant evolution, contributing to the origin of many new species. It can lead to rapid genetic diversification, the development of novel traits, and increased vigor or adaptation. Many economically important crops, such as wheat, cotton, and tobacco, are allopolyploids. While less common, allopolyploidy has also been observed in some animal lineages, though it is generally considered more challenging for animals due to more complex genetic and developmental systems.