At this point esch chromosome consist of a pair of chromatids and the two associated chromosomes are termed a tetrad.此时每条染色体由一对染色单体构成,这两条联合的染色体称为四分体.Microspore abortion occurred after the tetrad formation.小孢子败育发生在四分体形成以后...
Ivins downplays the idea of silver - suited space travelers.艾文斯对[空人银制衣裳]点子并不看好.After a short rest the travelers pushed on towards the coast.旅行者稍稍休息后,继续朝着海岸行进.Numerous travelers head for Elk, and other north coast getaway...
Draw your child's outline with a heavy black marker.用浓黑色的毡笔画出你孩子的轮廓。He placed a marker where the ball had landed.他在球落地的地方放了个标记。Step off twenty feet and then place a marker in the ground.先步测20英尺,再在地上做出标记....
他把那些断片切碎，然后把它们焊在一起。He cuts the pieces and solders them together.这些零件完好地焊在一起了.The parts welded together perfectly.在这样的温度下焊钢需要速度和技术.It takes speed and skill to weld steel at this heat....