kolloidy

Kolloidy, in biology, describes the state in which the cells of an organism possess more than two complete sets of chromosomes. It is a broader term that encompasses polyploidy, where the ploidy level is an exact multiple of the haploid genome. Kolloidy is especially common in plants, and less frequent but known in certain animal lineages.

There are two main forms: autopolyploidy, arising from genome doubling within a species; allopolyploidy, formed by hybridization between species followed by chromosome doubling. A related concept is endopolyploidy, in which specific tissues contain polyploid cells due to endoreduplication without whole-organism polyploidy.

Mechanisms of kolloidy include unreduced gametes (meiotic errors), somatic genome duplication during development, and cell fusion. In plants, polyploidization is a major driver of speciation and diversification and can occur rapidly in response to ecological pressures or mating barriers.

Consequences of kolloidy include larger cell and organ size, altered metabolism, and changes in gene expression. Fertility may be reduced in some polyploids due to meiotic irregularities, but allopolyploids can be fertile because of compatible chromosome pairing. In agriculture, polyploid crops include wheat (hexaploid), cotton (tetraploid), and strawberries (octoploid). Seedless fruits often arise from triploidy, such as some seedless watermelons.

Detection and study of kolloidy rely on methods such as flow cytometry to estimate DNA content and cytogenetics or genome sequencing to confirm ploidy level. Kolloidy has implications for evolution, ecology, and breeding strategies in both natural populations and crop improvement programs.