This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Every time a cell divides, its chromosomes must be distributed correctly between the two daughter cells. Central to this process is the centromere, a specialized region of the chromosome.
The centromere serves as the attachment site for the cellular machinery that pulls the chromosomes apart. Centromeres thus perform an essential function in cell division that emerged very early in eukaryotic evolution. Remarkably, although this function has been retained over almost 2 billion years of evolution, the DNA sequences underlying centromeres have evolved at an extraordinarily rapid rate.
An international team led by Dr. Korbinian Schneeberger, a professor and head of the Institute of Crop Biology at HHU, has now discovered how relatively small mutations can give rise to the enormous differences between centromeres. Their paper is published in Nature.
While the fundamental function of centromeres is highly conserved, their DNA sequences are not: Centromeres can differ dramatically between species and even between individuals of the same species. This apparent contradiction is known in biology as the "centromere paradox" and raises the question of how a structure that has retained such an ancient function can contain DNA that changes so rapidly. The research team used the model plant thale cress (Arabidopsis thaliana) to directly investigate the mutations that occur within centromeres from one generation to the next.
The study showed that centromeres exhibit a characteristic pattern of mutation: Point mutations—changes affecting just a single nucleotide, essentially one "letter" of the genome—occur at an almost tenfold higher rate than in the chromosome arms. Insertions and deletions also occur frequently, typically involving hundreds to several thousand DNA letters. These mutations are not random disruptions of the centromere.
In Arabidopsis, centromeres consist largely of a basic DNA sequence approximately 178 letters long that is repeated thousands of times. The newly identified insertions and deletions almost always added or removed complete copies of these repeat units, thereby maintaining the centromere's repetitive architecture. "Centromeres are far more dynamic than one might expect for a region of the genome with such an essential function," said Xiao Dong, a doctoral researcher at the MPIPZ and first author of the study.
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