We recently described, in Cannabis sativa, the oldest sex chromosome system documented so far plants (12–28 Myr old). Based on estimated age, we predicted that it should be shared by its sister genus Humulus, which is known also to possess XY chromosomes. Here, used transcriptome sequencing of an F1 family H. lupulus identify and study chromosomes this species using probabilistic method SEX-DET...

Heterogametic sex chromosomes have evolved independently in various lineages of vertebrates. Such sex chromosome pairs often contain nonrecombining regions, with one of the chromosomes harboring a master sex-determining (SD) gene. It is hypothesized that these sex chromosomes evolved from a pair of autosomes that diverged after acquiring the SD gene. By linkage and association mapping of the SD...

In diploid organisms each body cell (or 'somatic cell') contains two copies of the genome. So each somatic cell contains two copies of each chromosome, and two copies of each gene. The exceptions to this rule are the sex chromosomes that determine sex in a given species. For example, in the XY system that is found in most mammals including human beings males have one X chromosome and one Y chro...

Background: Newborn gender ratio is one of the most important factors in livestock industry. This ratio has affected on economic condition and controls sex-linked genetically transferred diseases. Offspring sex ratio is affected by such various factors. One of these factors is the Y to X bearing sperm ratio in normal semen that is called primary sex ratio, season and individual differences are ...

The heterogametic sex chromosomes (i.e. mammalian Y and avian W) do not usually recombine with the homogametic sex chromosomes which is known to lead into rapid degeneration of Y and W due to accumulation of deleterious mutations. On the other hand, some 96% of amphibian species have homomorphic, i.e. non-degenerate Y chromosomes. Nicolas Perrin's fountain-of-youth hypothesis states that this i...

All snake species exhibit genetic sex determination with the ZZ/ZW type of sex chromosomes. To investigate the origin and evolution of snake sex chromosomes, we constructed, by FISH, a cytogenetic map of the Japanese four-striped rat snake (Elaphe quadrivirgata) with 109 cDNA clones. Eleven of the 109 clones were localized to the Z chromosome. All human and chicken homologues of the snake Z-lin...

The unusual sex chromosomes of platypus are not homologous to the human X and Y chromosomes, implying that the sex chromosomes of placental mammals evolved after the monotreme and placental mammal lineages split about 165 million years ago.

Most mammalian species have heteromorphic sex chromosomes in males, except for a few enigmatic groups such as the mole voles Ellobius, which do not have the Y chromosome and Sry gene. The Ellobius (XX ♀♂) system of sex chromosomes has no analogues among other animals. The structure and meiotic behaviour of the two X chromosomes were investigated for males of the sibling species Ellobius talpinu...

Recombination suppression leads to the structural and functional differentiation of sex chromosomes and is thus a crucial step in the process of sex chromosome evolution. Despite extensive theoretical work, the exact processes and mechanisms of recombination suppression and differentiation are not well understood. In threespine sticklebacks (Gasterosteus aculeatus), a different sex chromosome s...