Crossing over The exchange of material between homologous chromatids by the formation of chiasmata.交换:同源染色单体之间形成交叉时遗传物质的交换现象.The exchange of prisoners of war was one of the key elements of the UN's peace plan.交换战俘是联...
With beating hearts, they descended through the hawthorns.于是他们怀着忐忑不安的心情, 穿过山楂丛,走下山坡.Some trees, such as junipers , cherries, and hawthorns, produce fruits that are eaten by birds.有些树种如桧柏 、 樱桃和山楂结出能被鸟类吞食的浆果.He had to deal...