Degeneration of Y
The very first verbal concept of Y chromosome degeneration (figure 1b) ended up being posted by Muller in 1914 31, not actually elaborated upon before the 1930s 38. Haldane 39 recommended that flowers must not experience Y chromosome degeneration towards the exact same degree as pets as a result of pollen selection within the haplotypic stage. Fisher criticized the theory that the Y should degenerate through 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 in the individual Y 48. This finding had been essential as it was once thought that intercourse ended up being decided by the amount of X chromosomes in mammals, with all 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 stages that are different the development of heteromorphic sex chromosomes, solidifying the theory that all Y chromosomes sooner or later degenerate. This changing view associated with the Y as possibly practical and evolutionarily labile sparked brand new theories of Y chromosome degeneration within 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. 继续阅读