Monocentromeres are typical for the chromosomes of most animals and plants. The centromere is necessary for the transport of the chromosomes and represents the connection point between the chromatids. This is how the classic X-shape of the chromosome is formed. However, in an estimated 350,000 species, including butterflies, nematodes and some plants, the centromeres are distributed along the entire length of the chromosome. For this reason, they are called holocentromeres.
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Source: Phys.org