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A surprising evolutionary story: How did holocentric chromosomes evolve independently in plants and animals?
In 1935, scientist Franz Schrader first described the existence of holocentric chromosomes, which are characterized by having multiple dynamin centers along their entire length, rather than a single centriole like normal chromosomes. This important discovery not only provides a new perspective for cell biology, but also helps us understand the diversity and evolution of chromosomes in different organisms.
Holocentric chromosomes are characterized by the lack of a major constriction corresponding to the centriole and by the presence of multiple dynamin centers evenly distributed throughout the chromosome axis.
The evolution of holocentric chromosomes is not accidental; their independent evolution in animals and plants suggests that these chromosomes have some kind of adaptive advantage. To date, about 800 different species of animals and plants are known to have this unique chromosome structure, including insects, plants, arachnids and nematodes.
The existence of holocentric chromosomes is important for stabilizing chromosome fragments and preventing chromosome loss due to double-strand breaks. This enables them to promote adaptation through genome recombination and mutation during the evolution of organisms. However, holocentric chromosomes also have their limitations, such as the effect on crossovers, which may result in a restricted number of crossovers in dizygotes.
According to current research, the emergence of holocentric chromosomes is likely due to convergent evolution with monocentric chromosomes.
In the animal kingdom, especially in the Oligoneoptera and Neoptera groups of insects, the formation of holocentric chromosomes may represent an evolutionary trend independent of monocentric chromosomes. This process shows how environmental pressures shape the chromosome structure of organisms and further influence their survival strategies.
For example, in some plant-eating insects, the presence of holocentric chromosomes is considered a defense mechanism against plant-produced compounds that cause DNA damage and thus destabilize chromosome segments. change.
Overall, holocentric chromosomes may, through their diverse evolutionary processes, reflect the selection pressures and adaptive strategies encountered in different biotic environments.
In plants, such as algae of the Nelumboales and some higher plants, the existence of holocentric chromosomes has been found. Taking the most studied fungus Luzula spp. as an example, its chromosomes can be broken apart under the influence of nature or radiation and still maintain the ability to survive. This feature also suggests that holocentric chromosomes play an important role in the evolution and genetic diversity of plants.
The phenomenon of "inverted meiosis" between different species, especially in the meiosis process of germ cells, further promotes the chromosomal diversity between different species and may promote the rapid evolution of species. .
The evolutionary trajectory of holocentric chromosomes provides new insights into how organisms make complex genetic choices in the face of environmental challenges.
These findings challenge the traditional understanding of chromosome evolution and make us begin to re-examine the chromosome diversity in the biological world and the biological significance behind it. In future research, how the holocentric chromosomes of various animals and plants respond to environmental changes will be a topic worthy of in-depth exploration. As science and technology advance, will we be able to gain a deeper understanding of these unique chromosome mechanisms and their amazing evolution?
