题干

染色体的断裂片段在有丝分裂时不能进入子细胞核中,而在细胞溶胶中形成圆形结构,称为微核。通过染色可观察到微核,常用含微核的细胞数占观察细胞总数的比例(微核率)来检测有毒物质对细胞的危害程度。某研究小组应用微核检测技术探究不同浓度的氯苯对人类细胞的危害程度。请根据以下提供的实验材料与用具,补充完成实验思路及其它小题。

材料和用具:人成纤维细胞悬浮液、培养液、0.1mg/L氯苯溶液、染色液、显微镜、细胞培养瓶、二氧化碳培养箱等。(染色和制作装片的具体方法不作要求)

上一题 下一题 0.0难度 选择题 更新时间:2019-04-22 06:03:06

答案(点此获取答案解析)

同类题4

阅读理解

    Poet William Stafford once said that we are defined more by the detours (绕行路) in life than by the narrow road toward goals. I like this image. But it was quite by accident that I discovered the deep meaning of his words.

For years we made the long drive from our home in Seattle to my parents' home in Boise in nine hours. We traveled the way most people do: the fastest, shortest, easiest road, especially when I was alone with four noisy, restless kids who hate confinement (限制) and have strong opinions about everything.

    Road trips felt risky, so I would drive fast, stopping only when I had to. We would stick to the freeways and arrive tired.

    But then Banner, our lamb was born. He was rejected by his mama days before our planned trip to Boise. I had two choices: leave Banner with my husband, or take him with me. My husband made the decision for me.

    That is how I found myself on the road with four kids, a baby lamb and nothing but my everlasting optimism to see me through. We took the country roads out of necessity. We had to stop every hour, let Banner shake out his legs and feed him. The kids chased him and one another. They'd get back in the car breathless and energized, smelling fresh from the cold air.

    We explored side roads, catching grasshoppers in waist-high grass. Even if we simply looked out of the car windows at baby pigs following their mother, or fish leaping out of the water, it was better than the best ride down the freeway. Here was life. And new horizons (见识).

    We eventually arrived at my parents' doorstep astonishingly fresh and full of stories.

    I grew brave with the trip back home and creative with my disciplining technique. On an empty section of road, everyone started quarreling. I stopped the car, ordered all kids out and told them to meet me up ahead. I parked my car half a mile away and read my book in sweet silence.

    Some road trips are by necessity fast and straight. But that trip with Banner opened our eyes to a world available to anyone adventurous enough to wander around and made me realize that a detour may uncover the best part of a journey—and the best part of yourself.