How many chromosomes contribute to sex determination in a copepod?


Sex without sex chromosomes: genetic architecture of multiple loci independently segregating to determine sex ratios in the copepod Tigriopus californicus. H.J. Alexander, J.M.L. Richardson, S. Edmands, B.R. Anholt

Here we confirm a polygenic architecture of sex determination in the copepod Tigriopus californicus.

QTL mapping of the sex ratio phenotype (or the proportion of males in the brood of F2 females) estimate at least six loci on five separate chromosomes are associated with sex ratio of a family.

We also report, for the first time in any polygenic sex determining system, that the sex ratio phenotype varied among loci across chromosomes in both direction and magnitude, with the strongest phenotypic effects on chromosome 10 moderated to some degree by loci on four other chromosomes. Sex ratio phenotype varied in magnitude for individuals derived from different dam lines.

These data, together with the environmental factors known to contribute to sex determination, characterize the underlying complexity and potential lability of sex determination in this species.

There was a big team involved in this project; we wish to thank you all for your many hours of work!