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Molecular and evolutionary dynamics of animal sex-chromosome turnover


Prevailing models of sex-chromosome evolution were largely inspired by the stable and highly differentiated XY pairs of model organisms, such as those of mammals and flies. Recent work has uncovered an incredible diversity of sex-determining systems, bringing some of the assumptions of these traditional models into question. One particular question that has arisen is what drives some sex chromosomes to be maintained over millions of years and differentiate fully, while others are replaced by new sex-determining chromosomes before differentiation has occurred. Here, I review recent data on the variability of sex-determining genes and sex chromosomes in different non-model vertebrates and invertebrates, and discuss some theoretical models that have been put forward to account for this diversity.

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Fig. 1: Putative steps in the evolution of heteromorphic sex chromosomes.
Fig. 2: A ‘trap’ model of sex-chromosome turnover and conservation.
Fig. 3: Convergent recruitment of sex-determining genes as new master switches of sex determination in vertebrates and insects.


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B.V. thanks the members of the Vicoso lab for their comments and suggestions on the manuscript. This work was supported by the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant agreement number 715257).

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Correspondence to Beatriz Vicoso.

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Vicoso, B. Molecular and evolutionary dynamics of animal sex-chromosome turnover. Nat Ecol Evol 3, 1632–1641 (2019).

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