Degeneration of Y
The initial theory that is verbal of chromosome degeneration (figure 1b) had been posted by Muller in 1914 31, however actually elaborated upon through to the 1930s 38. Haldane 39 recommended that flowers must not experience Y chromosome degeneration to your exact same level as pets as a result of pollen selection when you look at the phase that is haplotypic. Fisher criticized the theory 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 male-determining element had been found regarding the human Y 48. This breakthrough ended up being essential since it once was assumed that intercourse had been decided by the sheer number of X chromosomes in mammals, because of the Y only a fragment that is non-functional (in line with Bridges’ studies in Drosophila 30).
Ohno 51 later suggested that the variation in intercourse chromosome morphology noticed 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. Read More