A method for determining sex and chromosome copy number: sex-by-sequencing reveals the first two species of marine mammals with XXY chromosome condition
Bibliographic record
Abstract
Abstract Molecular assays of sex determination typically rely on qualitative evaluation of sex-linked markers, which can lead to uncertainty when results contradict morphological identifiers of sex. To investigate whether disagreement between phenotypic and genotypic assays of sex could be underpinned by variation in sex chromosome copy number, we developed a quantitative genetic method to determine sex that is broadly applicable to mammals with XY sex determination. We sequenced a region of the zinc-finger gene ZF, which has fixed genetic differences between the X and Y chromosomes, and screened 173 cetacean specimens for ZFX–ZFY haplotype identity and read depth. Using a subset of 90 male specimens, we demonstrate that haplotype read depth is an accurate estimator of chromosome copy number. We identified three specimens representing two different cetacean species that had external female morphological traits, Y chromosome haplotypes, and ratios of ZFX:ZFY haplotypes that were above the 1:1 value expected for genetic males. These results provide the first evidence of XXY aneuploidy in cetaceans. Investigation of the reproductive tract of one specimen, a True’s beaked whale (Mesoplodon mirus), revealed an intersex phenotype; despite having external characteristics typically diagnostic for the female sex, a penis and testes were present. Our results suggest that intersex phenotypes may be associated with XXY aneuploidy, and that this phenomenon may be underestimated due to it not being detectable by qualitative assays for determining sex.
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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 | 0.001 | 0.001 |
| 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 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".