题目

下列对于遗传和变异的认识正确的是( ) A．基因自由组合定律的实质是：F1产生配子时，等位基因分离，非等位基因自由组合 B．非同源染色体之间染色体片段的交换属于染色体变异 C．基因型Dd的豌豆经减数分裂会产生雌雄各两种配子，雌雄配子比例为1:1 D．利用八倍体小黑麦的花药组织培养出来的植株是四倍体 Working abroad for many years, he has made a big _______ and started a company of his own.A．difference B．fortune C．progress D．breakthrough