Plants with 2 Y chromosomes suffer infertility, but not inviability, perhaps because XX individuals that produced male flowers had an advantage in establishing populations in the past. Or YY plants have abnormal gene dosage.
The Y chromosome of Mercurialis annua is homomorphic yet 1/3 is not recombining and is enriched in sex-biased genes, perhaps a sign of ongoing sexual antagonism.
No YY plants are produced when the Y is wild type, confirming the Y is significantly degenerated.
The level of sexual dimorphism depends on the environment where Silene latifolia grows. We are looking for QTL based on a cross between plants from dry and wet environments, with a special interest to QTL that localise on the sex chromosomes.
Lines with large and small flowers (good for females and males, respecively) have been generated by artificial selection. Gene expression differences between those lines should reveal the first genes that respond to such sexually antagonistic selection.
Confirmation of male-specific PCR markers in the annual plant Mercurialis annua.
Incomplete penetrance of sex determination in frogs, and achiasmatic meiosis in males, allows for interesting possibilities in the evolution of a new sex chromosome.