Degeneration of Y
The initial theory that is verbal of chromosome degeneration (figure 1b) ended up being posted by Muller in 1914 31, yet not actually elaborated upon before the 1930s 38. Haldane 39 recommended that flowers must not experience Y chromosome degeneration towards the exact exact exact same degree as pets as a result of pollen selection within the phase that is haplotypic. Fisher criticized the theory that the Y should degenerate via the accumulation of recessive lethals and predicted (wrongly) that the X and Y should harbour equal amounts of life-threatening mutations 40. In 1959, a factor that is male-determining found regarding the individual Y 48. This development had been essential given that it once was thought that intercourse had been dependant on the amount of X chromosomes in mammals, aided by the Y merely a non-functional fragment 18 (in line with Bridges’ studies in Drosophila 30).
Ohno 51 later on suggested that the variation in intercourse chromosome morphology present in snakes corresponds to various phases in 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 new theories of Y chromosome degeneration when you look at the 1960s and 1970s and finally generated a debate within the 1990s and 2000s over whether or not the individual Y chromosome will eventually vanish 69,70.read more