Male heterogamety Female heterogamety X chromosome Y chromosome Z chromosome W chromosome Associations with sexually dimorphic phenotypic traits Size dimorphism in red deer Foerster et al. For example, if genes essential for male sexual fitness are closely linked to the old Y chromosome, then the spread of a new sex-determining factor can be retarded as sex chromosomes differentiate and turnover can be even more unlikely.
This creates a gene imbalance between males and females, with the heterogametic sex having just one copy of X- or Z-linked genes. Ranz JM, et al. Even more interesting, species with alternative reproductive cycles show deviations from the general pattern of sexualization that are entirely consistent with expectations, as observed with the masculinization of the pea aphid X chromosome, which is caused by its unique inheritance between males, sexual females, and parthenogenic females Jaquiery et al.
Trends Ecol Evol 24 : —
Bioessays 33 : — A genetic basis for a postmeiotic X versus Y chromosome intragenomic conflict in the mouse. Sex chromosomes and speciation in Drosophila. Locus positions are based on the G. Notes 5—
Nonetheless, there is evidence of a rapid expansion in copy number of these sex-linked genes during the past 3 million years, and it is suggested this is caused by the antagonistic conflict that the X and Y chromosomes are locked into Good Bibcode : PNAS.
Harvard: Belknap Press. This would mean that selection in XY males to up-regulate dosage-sensitive X-linked genes would override the cost of overexpression in XX females, but selection in ZW females to hyperexpress similar genes on the Z chromosome would be retarded by selection against overexpression in ZZ males Mank SGEs and their corresponding suppressors are therefore locked in an ongoing antagonistic arms race.
In stark contrast, complete Z chromosome dosage compensation has yet to be seen in any female heterogametic species Itoh et al. This is because sexual conflict on the autosome can select for sex-linkage, which may explain the formation of a neosex chromosome in the Japan Sea population of three-spined sticklebacks, Gasterosteus aculeatus Kitano et al.
Journal of Theoretical Biology.
Ohtani, H. Wagner Molecular Ecology Genome-wide patterns of divergence and introgression after secondary contact between Pungitius sticklebacks Yo Y. Solari AJ.