Since crossing over can occur during the first meiotic division, it does allow for some genetic variation in the offspring. 在第一次減數(shù)分裂的過程中可以發(fā)生交換現(xiàn)象，因而在后代中有遺傳變化。
It followed a normal course up to first meiotic metaphase when it inexplicably failed. 它按正常減數(shù)分裂過程進(jìn)行到第一次減數(shù)分裂中期后就莫名其妙地停止了。