Relationships between Vertebrate ZW and XY Sex Chromosome Systems

Relationships between Vertebrate ZW and XY Sex Chromosome Systems

The peculiar cytology and unique evolution of sex chromosomes raise many fundamental questions. Why and how sex chromosomes evolved has been debated over a century since H.J. Muller suggested that sex chromosome pairs evolved ultimately from a pair of autosomes. This theory was adapted to explain variations in the snake ZW chromosome pair and later the mammal XY. S. Ohno pointed out similaritie...

XY and ZW: Is Meiotic Sex Chromosome Inactivation the Rule in Evolution?

The sex chromosomes are among the most rapidly evolving and most diverse genetic systems in all of biology. Students of model organisms may, however, have the false impression that there is only one chromosomal mechanism of specifying sex. Among the best-studied metazoans, the XY system is indeed the rule, with inheritance of two X’s determining the female sex (XX), and inheritance of an X and ...

Sex-chromosome chimerism (XX-XY) in heterosexual bovine triplets.

Evolutionary transitions between mechanisms of sex determination in vertebrates.

Sex in many organisms is a dichotomous phenotype--individuals are either male or female. The molecular pathways underlying sex determination are governed by the genetic contribution of parents to the zygote, the environment in which the zygote develops or interaction of the two, depending on the species. Systems in which multiple interacting influences or a continuously varying influence (such ...

Mapping Chromosome Evolution between Species

Sticklebacks are small fish that inhabit fresh water and marine environments throughout the Northern Hemisphere. They are established models for the study of species evolution (speciation) and are more recent subjects for the study of chromosome rearrangements, as the chromosomes of the six species within the stickleback family differ in both number and morphology (shape/size). These difference...