# Y chromosome is lost more often in first divisions of mouse embryos, slowing cell division

- Published: 2026-11-07 20:04 UTC
- Section: Life & Health › Biology & biochemistry
- Tags: Y chromosome loss, early mouse embryo, Y centromere, kinetochore strength, chromosome missegregation, mosaic embryos, aggregation model, Turner syndrome XO, male sex determination
- URL: https://realtech.media/news/rt-38b052b14e62855a8a27907b_y_chromosome_is/

**Authors report the Y centromere is unusually weak in the first embryonic mitoses of mice, and Y loss slows cell division and reduces embryo size.**

![Y chromosome is lost more often in first divisions of mouse embryos, slowing cell division](https://realtech.media/media/2026/11/b9a671f101bdbec8.jpg)
*McDole et al., Wikimedia Commons, CC BY 4.0*

Researchers described in Science Advances a window in the first mitoses of the mouse embryo during which the Y chromosome is especially prone to loss. The Y lacks canonical centromeric repeats needed for high-fidelity segregation, and in adult tissues this causes Y loss [1]. In the early embryo, the authors found the Y centromere unusually weak [1].

This weakness impairs kinetochore strength, and the Y becomes preferentially trapped at the spindle pole, leading to missegregation [1]. To study the effect, the team built an aggregation model that tracks specific aneuploidies in mosaic embryos. Loss of the Y slowed cell division and reduced embryo size [1].

The authors link the findings to male sex determination and to the origin of Turner syndrome (XO). The work was done in mouse embryos.

## Sources

1. [Science Advances](https://doi.org/10.1126/sciadv.aej3098)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-38b052b14e62855a8a27907b_y_chromosome_is/