Zentromers

Zentromers are a theoretical class of chromosomal regions proposed in speculative biology and science fiction to serve as an alternative to conventional centromeres. The term Zentromer combines a prefix suggesting centrality with centromer, to denote a central chromosomal element defined by a distinct protein assembly rather than a fixed DNA sequence.

In proposed models, Zentromers are defined by an epigenetic identity established by specialized histone variants and kinetochore-like protein complexes. Unlike canonical centromeres that are often defined by repeat-rich DNA motifs, Zentromers rely on a dynamic chromatin state that can be established at different loci on a chromosome and can be inherited through cell divisions.

Functionally, Zentromers are imagined to anchor kinetochores and mediate attachment to spindle fibers during mitosis and meiosis, enabling proper chromosome segregation. They may exhibit greater flexibility in positioning than standard centromeres, potentially allowing rapid evolutionary rearrangements while preserving genome stability in the model organisms envisioned.

Status: Zentromers have not been observed in real organisms. They are discussed primarily in theoretical works on chromosome architecture and in speculative fiction as a device to explore alternative inheritance mechanisms, recombination suppression, and genome organization. Critics argue that the strict inheritance physics of real centromeres would pose significant hurdles for a functional Zentromer system.

Further reading and related concepts include centromere, kinetochore, epigenetic identity, and neocentromere.