Degeneration of Y
The initial theory that is verbal of chromosome degeneration (figure 1b) ended up being posted by Muller in 1914 31, however actually elaborated upon before the 1930s 38. Haldane 39 recommended that flowers must not experience Y chromosome degeneration towards the exact same extent as pets because of pollen selection into the phase that is haplotypic. Fisher criticized the concept that the Y should degenerate through the accumulation of recessive lethals and predicted (improperly) that the X and Y should harbour equal variety of life-threatening mutations 40. In 1959, a factor that is male-determining found from the individual Y 48. This breakthrough ended up being crucial since it once was thought that intercourse had been dependant on the sheer number of X chromosomes in mammals, utilizing the Y just a fragment that is non-functional (in line with Bridges’ studies in Drosophila 30).
Ohno 51 later on suggested that the variation in intercourse chromosome morphology observed in snakes corresponds to stages that are different the development of heteromorphic sex chromosomes, solidifying the concept that all Y chromosomes sooner or later degenerate. This changing view of this Y as possibly practical and evolutionarily labile sparked brand new theories of Y chromosome degeneration when you look at the 1960s and 1970s and finally generated a debate when you look at the 1990s and 2000s over or perhaps a human Y chromosome will eventually vanish 69,70.