某夫妇妻子色盲,丈夫表现型正常,生下一性染色体组成为XXY的色肓孩子,出现这种现象的原因可能是 A.女方减数第一次分裂异常或减数第二次分裂异
阅读下面的文字,按要求作文(50分) 一段时间以来,“中学生有三怕,奥数、英文、周树人”成了校园流行语。实际情况是,有些同学有这“三怕”
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The school _____ a 20-classroom building which was put up last year lies near the town. A. hasB. where C. with D. in which
正常人的卵细胞中的染色体应表示为 A.22对+XX B.22条+X C.22条+Y D.22对+XY
It was one of the hottest days of the dry season. It had not rained in almost a month. The crops were dying. Cows had stopped giving milk. If it did not rain soon, we would lose everything. On this
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