Evidence for Different Origins of Sex Chromosomes in Closely Related Oryzias Fishes: Substitution of the Master Sex-Determining Gene
Bibliographic record
Abstract
The medaka Oryzias latipes and its two sister species, O. curvinotus and O. luzonensis, possess an XX-XY sex-determination system. The medaka sex-determining gene DMY has been identified on the orthologous Y chromosome [O. latipes linkage group 1 (LG1)] of O. curvinotus. However, DMY has not been discovered in other Oryzias species. These results and molecular phylogeny suggest that DMY was generated recently [approximately 10 million years ago (MYA)] by gene duplication of DMRT1 in a common ancestor of O. latipes and O. curvinotus. We identified seven sex-linked markers from O. luzonensis (sister species of O. curvinotus) and constructed a sex-linkage map. Surprisingly, all seven sex-linked markers were located on an autosomal linkage group (LG12) of O. latipes. As suggested by the phylogenetic tree, the sex chromosomes of O. luzonensis should be "younger" than those of O. latipes. In the lineage leading to O. luzonensis after separation from O. curvinotus approximately 5 MYA, a novel sex-determining gene may have arisen and substituted for DMY. Oryzias species should provide a useful model for evolution of the master sex-determining gene and differentiation of sex chromosomes from autosomes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".