Staggered twins: scientists show the shape of replicated chromosomes is asymmetrical

Scientists in the labs of Anton Goloborodko and Daniel Gerlich at the Institute of Molecular Biotechnology (IMBA) of the Austrian Academy of Sciences have discovered that replicated chromosomes are not perfectly symmetrical: their two identical copies are consistently offset. Published in Science, the finding has implications for how cells repair damaged DNA and safeguard their genome.

Image: Following DNA replication, sister chromatids (red and blue) are consistently shifted relative to one another, placing corresponding DNA regions (yellow) out of alignment. Cohesin rings (green) maintain this arrangement. Generated with ChatGPT by Anton Goloborodko.

Ask anyone to picture a chromosome, and they will likely picture an X. That iconic shape appears only briefly, just before a cell divides: two identical molecules, called chromatids, held together, perfectly mirroring each other. Scientists in the labs of Anton Goloborodko and Daniel Gerlich at the Institute of Molecular Biotechnology (IMBA) of the Austrian Academy of Sciences now find that earlier in the cell cycle, sister chromatids are not aligned mirror images at all: they are systematically offset from one another. This fundamental discovery, now published in the journal Science, reveals hidden asymmetry, with implications for how cells repair damaged DNA and safeguard their genome.

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Original publication: 

Conformational asymmetry of replicated human chromosomes. Flavia Corsi, Thomas L. Steinacker, Sofia Kolesnikova, Zsuzsanna Takács, Paul Batty, Michael Mitter, Daniel W. Gerlich*, Anton Goloborodko*. Science, 2026. DOI: 10.1126/science.aea4611

*co-corresponding authors 

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